Mensuration
Mensuration
(vi) Diagonal = √
SOLIDS                                                        CUBE
A solid has three dimensions, namely length, breadth or       A cube is a solid figure having six faces. All the faces of a
width, and height or thickness. The plane surfaces that       cube are equal squares (let us say of the side ‘a’).
bind it are called its faces and the solid so generated is    Therefore, the length, breadth, and height of a cube are
known as polyhedron.                                          equal.
The volume of any solid figure is the amount of space                   (i) Volume = a3
enclosed within its bounding faces. A solid has edges,                 (ii) Lateral surface area (LSA) or area of the four
vertices, and faces, which are shown in the figure.                                 walls = 4a2
A solid has the following two types of surface areas:                  (iii) Total surface area (TSA) = 6a2
Lateral Surface Area Lateral surface area (LSA) of a          (iv) Diagonal = a √
solid is the sum of the areas of all the surfaces it has
except the top and the base.                                  RIGHT CIRCULAR CYLINDER
Total Surface Area Total surface area (TSA) of a solid
is the sum of the LSA and the areas of the base and the
top.
Note: In case of solids, like the cube and cuboid, the LSA
consists of plane surface areas (i.e., area of all surfaces
except the top and base), whereas in case of solids, like
cone and cylinder, it consists of curved surface areas
                                                              In the above figure, r is the radius of the base and h is the
(CSA). Therefore, for such solids, the LSA is also called
                                                              height of a right circular cylinder. A cylinder is generated
CSA.
                                                              by rotating a rectangle or a square by fixing one of its
                                                              sides.
Euler’s Rule
                                                              (i) Volume = area of base × height
                                                              (ii) Volume = r2 h
Euler’s rule states that for any regular solid:
                                                              (iii) Curved surface area (CSA) = Perimeter of base ×
Number of faces (F) + Number of vertices (V) = Number
                                                                                height
of edges (E) + 2
                                                              (iv) LSA = 2 rh
                                                              (v) Total surface area (TSA) = LSA + area of the top +
CUBOID                                                                 area of the base
A cuboid is a rectangular solid having six rectangular        (vi) TSA = 2 rh + r2 + r2
faces. The opposite faces of a cuboid are equal               (vii) TSA = 2 r(r + h)
rectangles. A cuboid has a length (l), breadth (b), and
height (h).                                                   Some Important Deductions
    Figure 1                       Figure 2
                                                              If the above rectangular sheet of paper (ABCD) is rolled
In Figure 2, ED is the diagonal of the cuboid. Moreover,      along its length to form a cylinder, then the radius (r) of
the area of the surface GDCH is x, the area of the surface    the cylinder will be (L/2n) and its height will be b and
HEBC is y, and the area of the surface GFEH is z.
                                                              volume of this cylinder =     , where l is the length of the
(i) Volume = Area of base × height = lbh                      rectangle.
(ii) Volume = √
(iii) Volume = xh = yl = zb
(iv) Lateral surface area (LSA) or area of the four walls
         = 2 (l + b) h
(v) Total surface area (TSA) = 2(x + y + z) = 2
Frustum of Cone
A cone whose top portion is sliced o by a plane which is
parallel to the base is called frustum of cone.
Formation of frustum:
                                                               Octahedron
                                                               An octahedron is a solid that has eight faces. All the faces
                                                               of an octahedron are equilateral triangles. An octahedron
                                                               has six vertices and 12 edges.
In the above figure, a1 is the area of the top face of the
frustum, a2 is the area of the bottom face of the frustum,
h is the height of the frustum, and l is the slant height of
the frustum.
(i) Volume = h               √
(ii) Lateral surface area (LSA) =             l
          where P1 and P2 are perimeters of the top and
the               bottom faces.
    (iii) Total surface area (TSA) = LSA + a1 + a2
HEMISPHERE
3.Cube
                                                                             Figure
                Figure                                            Nomenclature  height
        Nomenclature  a = edge/side                              Volume  1/3 area of the base × Height
Volume                                                           Curved/Lateral surface area  1/2
Curved/Lateral surface area                             ×Perimeter of                                   the
Total Surface area                                      base × Slant height
                                                                  Total Surface area  Lateral surface area +
                                                         Area                                            of
3. Right circular cylinder                               base
7. Sphere
                  Figure
        Nomenclature  R = radius of base, h = height
of                     the cylinder
Volume        h
Curved/Lateral surface area                                                Figure
Total Surface area  2                                         Nomenclature  r = radius
                                                         Volume 
4. Right circular cone                                   Total Surface area 
8. Hemisphere
                  Figure
          Nomenclature  r = radius, h = height,
l = slant height,                                                           Figure
l=√                                                            Nomenclature  r = radius
                                                         Volume 
Volume 
                                                         Curved/Lateral surface area 
Curved/Lateral surface area 
                                                         Total Surface area 
Total Surface area 
5. Right triangular prism                                9. Spherical Shell
                                                                          =√
                                                                          = √(     ) =
                                                                  5.      (b) Perimeter of square = 44 cm
                                                                          4 × side = 44
1.   (b) Side of square =                                                 side = 11 cm
                                  √
                                                                          area of square = side2 = 112 = 121 cm2
     Area of square =
                              √                                           Circumference of circle = 44cm
                                                                          2 π(radius) = 44
     =                                                                    radius =
                                                                          area of circle =                     cm2
      = 2.6 × 5.2 = 13.52 cm2
                                                                          Option (b) is the answer. (circle, 33 cm2)
2.   (c) Area of square                                           6.      (b) Let the side of square = a
                                                                          and the radius of circle = r
      =            =
                                                                          perimeter of square = circumference of circle = 4a
                                                                           = 2πr
                                                                          r =
3.   (a) Let the length of rectangular hall = x
     Thus, Breadth of rectangular hall                                    area of circle = 3850 m2
      =                                                                   π×
     According to Question,                                               16a2 =                 , a2 = 3025m2
     Area = 768 m2                                                7.      (b) 2(l + b) = 28
     x×                                                                    l + b = 14
                                                                          and l × b = 48
                                                                          (l + b)2 = l2 + b2 + 2lb
                                                                          (14)2 = l2 + b2 + 48 × 2
                                                                            196 – 96 = l2 + b2
     = 256 × 4                                                            l2 + b2 = 100
     x =√                                                                 √( l2 + b2) = 10
      = 32m                                                               Diagonal = 10m
     Difference of length and breadth                             8.      (c) Let the length of rectangular hall = x
     =x–                                                                   Thus, Breadth of rectangular hall
                                                                          =
                                                                          According to question,
4.   (c) Since the room is in cuboid shape =                                Area = 192m2
     Length of largest rod = = Diagonal of cuboid                         x ×
     = √(                 )
         = √(                 )                                            x2 -       = 64 × 4
     √(                       )                                           x = √(64 × 4) = 16 cm
                                               32 m
                                                                           10             180       200
                                                                                    200
                            38 m
                            2
      area of path = 600 m
                                                                  Area of path = 200 × 220 – 200 × 180
       (l + b – 2x) = 600
                                                                   = 44000 – 36000 = 8000 m2
      (38 + 32 - 2x)2x = 600
                                                            34.   (c) Diagonal of square = diaeter of circle
      (70 + 2x)2x = 60
                                                                   =8×2
       (70 – 2x)x = 600/2 = 300
                                                                  = 16 cm
      70x – 2x2 = 300
      2x2 - 70x + 300 = 0                                         Thus, Side of square = 16/√
      x2 – 35x + 150 = 0                                          → Area of square √ 2
      x2 - 30x + 5x + 150 = 0                                     = 128 cm2
      x (x – 30) – 5 (x - 30) = 0                           35.                           √
                                                                  (a) Side of square =        = 8 cm
                                                                                          √
       (x – 30 )(x - 5) = 0
                                                                  Thus, Area of square = 8 × 8 = 64 cm2
       x = 30 not possible
                                                            36.   (a) x2 + 7x + 10 = x2 + 5x + 2x + 10
      x = 5 (right)
                                                                  = x(x + 5) + 2 (x + 5)
29.   (c) Area of walls = Perimeter of base × height = 18
                                                                   = (x + 2) (x + 5)
      × 3 = 54 m2
                                                                   Thus, Two sides of rectangle
      a =9
                                                                  = (x + 2) (x+ 5)
30.   (d) a2 = 81, a = 9
                                                                  Thus, Perimeter = 2(x + 2 + x + 5)
      → Perimeter of square
                                                                  = 2 (2x + 7) = 4x + 14
        =9×4
                                                            37.   (c) Let the sides of rectangle be 6 cm and 2 cm (or
        = 36 cm
                                                                  any other number)
        → 2r + π r = 36
                                                                  → Area of rectangel Q = 6 × 2
       r (r + π ) = 36
                                                                   = 12 cm2
4m
                                        12 cm                  B           F              C
                                                                      2     2    2
                                                              Thus, 3 + 4 = 5
                                                              ABC is a right angled triangle
                                                              ar(ABC) =
                        15 cm                                                 cm2
      Areao fthe triangel =                                   thus, Requred Area of (Δ DEF)
      = +1/2 × 15 × 12                                        =             cm2
       = 90 cm2
      Area of another triangle = 2 × 90 = 180 cm2             =                    cm2
67.
3.5 3.5 7 cm
                                                                                B                                   C
                                     28 cm                                                          2r
Circumm radius
                       r = 20
                       cm
                                                                      x                            5 cm
      whell of radius 20 cm no. of revolutions
                                                                      B                 C
      =                                                           isoceleus right traingle
                                                                  Thus, x2 + x2 = 52 = 25
86.   (a)
                                                                  Area of trinagle
                       A
                                                                    =   x2 =                                   cm2
                                                            89.   (c)           A
                  P1 P3
                        P2                                                      6 cm 8 cm
      B                   C
                                                                                         7cm
      In an equilatera triangel
      side = (P1+ P2+ P3)                                         B                                    C
                  √
87.   (c)                                                         Length of side =                      (P1 + P2 + P3 )
                                                                                                   √
                                                                  =
                                                                      √
                                                                   =
                                                                          √
                                                                                 √                 √
                                                                   =
                                                                          √      √
                                                                   = 14√3 cm
                                                            90.   (c) Remember : area of isoceleus triangle
                                                                   = a2 sin θ (θ is angle between equal sides)
            4√3                                                   =           (10)2 × sin 45°
                                                                                                        √
                                                                                     √         √        √
                                                                   = 25√2 cm2
      side of equilateral triangle                          91.   (a)
      = 4√3
                                             √
      Ccircumradius of traingle =                =4
                                         √   √
      See the figure                                                                           o A E C
      side of square = 2 × circum radius
      =2×4 =8
                                                                  Radius of circule = 6 cm
                                                                  Area of smallest circle =                           = 12 π
                      8√2            8
                                                                  Radius of smallest circle
                                                                          √
                                                                   =                 = 2√3 cm
                                                                                    2a        a
                                    a
              B                          C
                                                                  Area of shaded region
      √       2                                                   = area of semicircle - area of triangle
         a = 4√3
          2
       a =4×4                                                      =
      a = 4 cm                                                    =       –a2 = a2 (       )
      Circum radius =                                       96.   (c) According to question
                            √        √
       Area of circle = πr2                                       π (R + 1)2 – π R2 = 22
      = π ( )2                                                    π ,(R + 1)2 - R2} = 22
              √
      =           cm2                                             (R + 1 + R) (R + 1 - R) =
93.   (b)                                                         2R + 1 = 7
                                                                  R = 3 cm
                                r                           97.   (b)
                                                                                   7cm               14 cm
      Circumference – diameter = 30 cm
      2πr – 2r = 30                                                          148 cm
      2r (π - 1) = 30                                             radius of lartgest circle
      r=
94.   (b)                                                         Area =                            cm2
                                                            98.
      12 cm
                                    13 cm                                                    8 cm
                                                                  =
       =                                                          = 16.76
95.   (c)                                                         Required area
                 cm2
99.    (c) 30 : 72 : 78                                              C          B           C
            5 : 12 : 13                                                   4            4
       So the trinagle is right tirangle                         The cone so formed after rotating about Side AB.
                                                                 So, slant height of cone
                                                                           = 5 cm
                                                                 radius     = 4 cm
       30                         78                                Height = 3 cm
                                                                 Thus, Volume of cone
                                                                 =       r2h
                            72                                   r = radius
                    =                                            h = height
       altitude = 30 m                                           Thus, Volume of cone
100.   (a)                                                        =
                                                                 = 16 π cm3
                                                          102.   (c)
       x                         √2x
                                                                                 1             1
                 x
       Perimeter of triangle                                                 1                     1
       = √
       x + x + √2x = 4√2 + 4                                                 1          1
       2x + √2x = 4√2 + 4                                        Area of bounded region
       x(2 + √2 ) = 4(√2 + 1)                                    √
                                                                         22 - π (1)2
        x =
                    √                                            =(√          )cm2
           Hypotenuse = √2x
                                                          103.   (a)
           =√
                                                                 2πr = 11
           =√
                        √                                         →r =
101.   (a)
                                                                 Area of sector
               A                                                             2
                                                                  =
       3                         5                                =            cm2
                                                          104.   (c) Let the side of the triangle be ‘a’ cm
                                                                 → Circumradius =
         B        4        C                                                               √
                    3            3
                    3            3                                B                   C
                                                              As P and Q are mid-point and PA
                   3       3                                  → Δ APQ – ABC
       Area orf shaded portion                                 → AP/AB = PA/BC =
       = 6 × 6 – π 32                                         → PQ =
       = 36 – 3π
                                                              → BC = 2PQ = 2 × 5
       = 9 (4 - π) cm2
                                                              = 10 cm
121.   (c) Radius of incircle
             √
                                                       126.   (c)
       =                                                               A
             √
        = 7 cm
       → Area = πr2 =
                                                                  P             Q
        = 154 cm2
122.   (d)
       Radius of incircle
                                                                B                 C
                     √                                        As PQ || BC
        √                                                     → Δ APQ – ΔABC
       Area = π r2
                                                              → APQ is also an equilatera Δ
        = 3π cm2
                                                                          √
123.           √                                              → Δ APQ =       (5)2
       (c)         a2 = 121 √3
                                                                 In Δ OMB
           B       D         C                                   OB = √(152 + 82) = 17 cm
       ar Δ AOE = 15 cm2                                         OB = OD = radius
        ar BOFD = 2 × ar Δ AOE = 30 cm2                          In Δ OND
129.   (b)                                                       ND = √(172 - 82)
                                                                  = 15 cm
                                                                 CD = 15 × 2
                                                                  = 30 cm
                                                          136.   (b) Perimeter = 2r + πr
                            A                                    = 63 +
                                                                 = 63 + 99 = 162 cm
                                                          137.   (c)             A
                    D               E
           B                      C
       ar ABE = ar Δ ACD = 36 cm2
130.   (a) The third side will be either 15 or
                                                                         B    D   F   E      C
       → Possible perimeter
                                                                 In triangle AFB
        = 15 × 2 + 22
                                                                 AF | BC
        = 52
                                                                  AF2 = AB2 – FB2 = 100 = 25
        and 22 × 2 + 15
                                                                 AF = 5√3
        = 59
                                                                  In triangle ADF
131.   (a)
                                                                  AD2 = AF2 + BF2
       No. of revolutions
                                                                 AD2 = 75 +         2
                                                                           √
                                                                  AD =
                        = 500
                                                          138.   (c) Let sides of trangel are, a,b, and c respectively
132.   (b) 2πr =                                                 Thus, Largest side given = 17 cm
                                                                 = Perimeter = a + b + c = 40 cm (given)
        →r =          = 0.7
                                                                 area = 60 cm2 (given)
       → Diameter = .14 cm                                       In such questions take the help of triplets which
133.   (b) 2π r =                                                from right angle trinangle
        →r =                    = 35 cm                                       A
                                              (4, 0)                              x =     =     =
                                                                                  Note: The ratio of area of two similar triangles is
                                                                                  equal to the ratio fo square of their corresponding
                                                                                  sides.
                                                                           168.   (d)
       3x + 4y – 12                                                                                       A
                                                                                       B             D                 C
       Thus, Cordinates of point A = (0,3)
       Point B = (4,0)                                                            AB = AC = BC
       Area of Δ OAB = × 4 × 3 = 6 sq. units                                      AB + BC + AC = 544
164.   (c) hight of equilateral Δ = 15 cm                                           BC BC + BC = 544
       √                                                                                              = 544
                                                                                          = 544
       side =
                     √                                                            BC=
                         √                2
       Area =                                                                      = 204
                                                                                  → AB = AC =
             √                        √
                 (           )2 =             ×                                   Area of Δ ABC = b/4 √(4a2 - b2)
                     √
        = 75√3 cm2                                                                Thus, Where = equal side
165.   (b) √      (side)2 = 9√4                                                   b = base
             2
       (side) = 9 × 4 = 36                                                        =     √         2
                                                                                                    - (204)]2
       side = √36 = 6 cm                                                          = 51 √(115650 - 41616)
       Length of median = √                        (side)                         = 51 √73984
         √                                                                        = 51 × 272
        =            √ cm
                                                                                  = 13872 cm2
       Note: In an equilatera triangle, length of median,
                                                                           169.   (d)            A
       angle bisector, altitude is equal to √3/2 sides
166.   (c) Clearly,
                                                                                              a               a
       12 cm, 16 cm and 20 cm from a triplet
                                                                                                        8
         3      4       5 → triplet
                                                                                     B            b      b        C
             ×4              ×4       ×4
                                                                                                  D
       12            16           20 → triplet
                                                                                  AB = AC = a cm
                                                                                  BD = DC = b cm
       They from a right triangle
                                                                                  Altitude of isoscles triangel is also median
       area of triangle = × 16 × 12 = 96 cm2                                      In right Δ ADC
                                                                                  AD2 = a2 - b2
167.   (c)           =            =                                               64 = a2 - b2 …… (i)
                                                                                  Perimeter = 64
                             b           b
                                 B                                                                         3/2 s            s
       x = AB = b + c
       y = BC = a + b
       z = AC = a + c                                                            B                                               C
       Thus, semi-perimeter,s
       =              =
        =                                                                Height of equilateral triangle
            √                        ]                                       √
                                                                         =
       =√
                                                                                         √
171.   (d) π R2 = π (10)2 + π (24)2
       R2 = 102 + 242 = 100 + 576                                                                  =                =                √3
                                                                                         √             √                √
        R = √676
         = 26 cm                                                  174.   (c)
172.   (c)               A                                                                    A                                                    D
                                                                         .
                    a                        M a                                  B            3                    C                E                     F
                                                                              3                        3                        3              4
                        o                                                Δ ABC - ΔDEF
                                                                                   ]
                                                                                   ]
                B                        C                                           =
                            a                                                                                                             2
                                                                             ar(ΔDEF =
       Let the side of equilateral triangle = ‘a’
                                                                  175.                                     ]
       and the side of square = ‘b’                                      (b)                               ]
       in circle radius of equilateral Δ
       =
            √
B C
                            o                  A
                                                                            Width
               C2               12
                                                                                      R
                                C
       AB = AC triangle drawn from the same point equal             Let radius of outer circle = R
       OB = OC = 3cm                                                and radius of inner circle = r
       OA = 12 cm                                                   2 π R 2 π r = 66
       ∠ABO = ∠ACO 90°
                                                                    2 R - r) = 66
       In ight ΔABO
       AB √        2 - 32   √                                        R -r =        =
       √                √                                           width = 10.5
       ar ABOC = 2 × ar (ABO) = 2 × × AB × OB                179.   (a)
                                                                    Perimeter of the circle =
        = 3√              √    cm2
                                                                    Circumference of circle =
                                                                    Let ‘R’ be the radius
177.
                                                                    ATQ
                        Q
                                                                    2π R – 2R = x
                                                                    2R (π - 1) = x
                    5                                               2R =
                                     13                             Diameter =
                    o                                  P            Thus, 2R = Diameter of the circle
                                                             180.
                        R
                                                                                          √
       ∠OQP = ∠ORP            °
       (radius is | tangent )
       and PQ = PR (tangent drawn from same point
       are equal)
       PQ      √ OP 2 - (OQ)2 √    3 - 52) = 12
ar of (PQOR) = 2 × ar (PQO)
                                                                                                 o
                                                                                         r               8
                                                                                          15
                        88                                                           A       M15 B
                                                                           AB = 30 cm
       Length of are =                                                     OM | AB and OM = 8
                                                                           Thus, AM = BM = 15 cm
                                                                           In right Δ OMA
                                                                           OA2 = OM2 + AM2
        r                    = 70 m
                                                                           OA2 = 289
182.   (A)                                                                 AO = √
                                                                           OA = 17 cm
                                                                           Radius of circle = 17cm
                   4, 5               3, 5                          185.   (c)
                C                            B                                         A
                4, 5                         4,5
                             5, 5    5, 5                                                            r       15 cm
                                A                                                 9 cm       r
                                                                                                     r
                                                                                     B                               C
       In Δ ABC                                                                                  12 cm
       Perimeter of ΔABC = (AB + BC + AC)                                  Since, 9 , 12, 15 forms a triplet
       = 2 (3.5 + 4.5 + 5.5)                                                                                             2
                                                                           area of Δ ABC =
         = (13.5 × 2) = 27
                                                                           In circle radius of triangle
183.   (c)      A                                                            =
                                                                            =
                                                                           Alternate:
                                                                           In a right triangle, with , P, B and H incircle radius
             15 m                   25 m                                   =
                                                                           Hence, r =
       D                          C                                                      B       B      C
                                                                                  In Δ ABC and Δ A’B’C’
                                                                                  ∠ C = ∠C common
                                                                                  ∠B ∠B Thus AB || AB
                        a/2           a
                                                                                     Δ ABC - Δ A’B’C
       √2a
                                                                                     (            )    (    )2
                                                                                         2 =¼
           A                  B
                                                                                     a Δ A’B’C
                                                                           189.   (b) Perimeter of square = 44 cm
       Let the side of square = a                                                 Area of square = ( )2 = 121 cm2
       in circle radius of square =                                               Circumference of circle = 2 π r = 44
                                                                    √             r =
       Circumcircle radius of square =
                                                                                → Area of circle = π r2 =        2
       Thus,                                   =    √       √                    = 154 cm,2
       = 1 : √2                                                                  Required difference = 154 – 121 = 33 cm
187.   (d)                                                                 190. (d)                     C
                            a
                    A     a a              C
               2a                              2a                                                                   B
                              B
                                                                                         A
       Hence, ABC is the equilateral triangle
       AB= BC = AC = ‘2a’ cm
                                  √                     √
       area of Δ ABC = (2a)2 = =        2
                                                                                    C                      B
                                      A’                                                      M
               A              25
                                                                                   A    8        4       B
                                       D
201. (b)
r = =
216. (b)
                                    R
                          R+4
                                                                                                 l
                                                                       r
                                                                                 90°
                                                                                       r
       Outer radius of Pool with concrete wall = (R + 4)
       According to question ,                                         According to the firgure,
                            2
       πR ×                    - π R2                                  → Perimeter = r +r+ l
                                                                       3→ 75 cm = 2r + Length of arc
       R2 ×           R2 + 16 + 8R – R2
              2
                                                                       → 75 cm = 2r +
       =          = 16 + 8R
                                                                        → r = 21 cm
                           4               A
                                                                                          d = 700 m
                       45°                                               The breadth of the path
                                                                         = (R - r)
                   3                       B       D                     = (364 – 350) cm
                                                                          = 14 cm
                                                                  221.   (c)
                                                                         According to the questions
       According to the question
       Area of sector OED
       = πr2 ×
                                                                                       r = 84 cm
        =π×4×4×
        = 2r m2
       Area of the sector OAB
        = π r2 ×     =π×3×3×
        =         m2
       So, Area of shaded protion = Area of OED – Area of
       OAB
       →
                                                                  In Δ AOB,
       →                                                          OB = √(102 - 62)
        →                                                         = √(100 - 36)
                                                                  = √64 = 8 cm
                                                                  Diagonal BD = 8 × 2 = 16 cm
230.   (b) Given                                           234.   (b)     A                  D
       → Area of square = 4
        Side2 = 4
       side = 2                                                                                  5m
       → Diagonal of square = radius of circle
       √2 side = r
       → r = 2√2
       → Area of circle = π r2                                        B                  C
       → π × (2√2)2             3                                 4 × side of rhombus = 40m
231.   (a)                                                        side of rhombus = 10 m
       We know that rhombus is parallegogram                      Since rhombus is also a parallelogram
                                                                  Therefore its area = base × height
       whose all four sides area equal and its diagonals
                                                                  = 10 × 5 = 50 m2
       bisect each other at 90°
                                                           235.             D                   C
       . A                         B
                  12         16
                                                                                         6
                                                                                                 10
             16                12                                                   o
                                                                             6
          D                         C
                         2        2                                     A                    B
       Thus, AB = √(16) + (12) = √400 = 20 cm
        = side of rhombus                                                        10
       Thus, Perimeter of the rhombus = 20 × 4 = 80 cm            Perimeter of Rhombus = 40 cm
232.   (d) If d1 and d2 are the lengths of diagonals of            4 × side = 40
       rhombus.                                                   side = 10 cm
       then,                                                      We know that diagonals of rhombus bisect each
                                                                  other at right angle,
       Perimeter = 2√(d12 + d22 )
                                                                  Therefore, In right Δ OAB
       = 2√(242 + 102)
       =2 √676                                                    OB2 = AB2 - OA2
       = 2 × 26 = 52 cm                                            = 102 - 62 = 100 – 36 = 64
233.   (c) 4 × side = 40 cm                                       OB = √64 = 8 cm
       (given)                                                    Diagonal BD = 2 × OB = 2 × 8
       d2 =
237.   (a)
                                                                                   60°
                                                                               D                   C
                                                                           In the above figure Δ ADC is equilateral triangel (as
                                                                           AC is angle bisector)
                                                                           → AC = 10 cm (smaller diagonal)
                                                                    241.   (c) Side of rhombus
                                                                           =
                     1                                                     We know that in a rhhombus = 4a2 = d12 + d22
       A regular hexagon consists of 6 equilateral triangle                →
                                                                             d22 = 4 × 252 - 142 = 2500 – 196
       area of regular hexagon                                             = 2304
                    √
        =6×              (side)2                                           → d2 = √2304 = 48 cm
            √                                                              → Area =       d 1 × d2
       6×           a2
                √                  2
                                                                                                   cm2
       =6×               × (2√3)
                                                                    242.   (d) Let the parallel sides be 3x and 2x
                √
       =6×               × 12 = 18√3 cm2                                   →
238.                                         √                             → 5x = 60
       (a) Area of Hexagon = = 6 ×               (side)2
                √
                                                                           x = 12
       =6×           (1)2                                                  → Sum of length of parallel sides
                √              √                                            = (3 + 2)× 12 = 60 cm
       =6×                         cm2
                                                                    243.   (c)     A                      B
239.   (a)
                                                                                            15
                A                        D
                                                                                               20       7
                                                                               D                    C
                         10
                                                                           Using Hero’s formula
27
F 12
                      A                     B
                                                                       D        E             C
                                            15                    Area of parallegogram
                                                                  = AE × DC
              F               12                                  = CF × AD
                                                                  AE × 36 = 12 × 27
                                                                  = AE = 9 cm
              D                         C                         Thus, Distance between bigger sides = 9 cm
                  E   18                                   249.   (a) In a rhombus
                                                                                  D               E
                B      5               C                               5
       OC = 4 cm                                                              3
       In Right Δ OBC
       OB2 = BC2 – OC2                                                  A                                  C
        = 5 2 - 42 = 9
       OB = √9 = 3                                                    Thus, DE | | AC
       BD = 2 × OB = 2 × 3 = 6 cm                                     Thus, BDE – ΔBAC
       Area of Rbombus
                               2
                                                                                  = 22/52     =
        =
                                                                      ar (trap ACED ) = ar(BAC) - ar(BDE)
       Note : in the question do not get confused with the            = 25 – 4 = 21
       words non – square its simply to clear that it is
       Rhombus.                                                       Thus,               =       = 21: 4
252.   (c)                                                     254.   (c)
                   A                  D                                               D                C
                B                      C
                                                                            A                                  B
                    = ( )2 =           =4:1                                     N            o           P         12
                                                                                                                        12
       Thus, ΔAOB - Δ COD
255.   (d)       A    40                       D
                                                                                A        M         B     A
                                   o
                                                                             B
                40                            40               40            ara of ABCD = 24      ar (ABCD) = 24
                                                                             Draw QM and PN and intersect them a O
                                                                             ar□ POQC =
                B          40            C               40
                                                                             Thus, area PQC =
       Let AC =4x and BD = 3x                                                PQC = 3
       Thus, OA = 2x and OB =                                                QMAD =
       In Right Δ OAB                                                        QAD =
       √*(2x)2 + ( )2] = 40                                                  ABP = 6
       4x2 + 9x2/ 2 = 402 = 1600                                             ar(PQC) + ar(QAD) ar(ABP) = 15
       16x2 + 9x2 = 1600 × 4                                                 ar(APQ) = 24 – 15 = 9 cm2
       25x2 = 6400                                                            Also
       x2 =                                                                             =
            √                                                                Thus, Always it will be 3 : 8
       x =        =
                                                                      258.   (b)                 A
       Thus, Ac = 4x = 4 × 16 = 64
        BD = 3x = 3 × 16 = 48
       area =                                                                                    12
       =
        = 1536 cm2                                                                  B                        D
256.   (a)                                                                                    o          9
A D
                                                                                                 C
                                                                             Let d1 = 24 cm
        B                      C               Q                             area of Rhombus = 216
                                                                                  d1 × d2 = 216
       in Δ ABC & Δ DCQ                                                      d2 =                    = 216
                                                                                                 2
       ∠ABC ∠ DCQ
       ∠ACB ∠DQC                                                             d2 =
       BC = CQ                                                               OA =    × d1 =
       ΔAABC ΔDCQ
                                                                             Thus,
       a Δ ABC a ΔDCQ
                                                                             Diagonals of Rhombus bisect each other at right
257.   (c) D         Q                  C          D
                                                                             angle
       C
        OB     √
       Thus, BD = 2 × OB
              √                                                 side of Rhombus =           =
           √ cm                                                 Let, AC = 2a
260.   (c) ) A                    D                             thus, OA =OC = a
                                                                CD = 2b
                                                                OB = OD = b
                        o                                       In right Δ OBC,
                                                                a2 + b2 =
                 8            6
                                                                4a2 + 4b2 = p2    ………. (i)
                                                                Also, 2a + 2b = m
                                                                On squareing, 4a2 + 4b2 + 2ab = m
              B       10        C                               4a2 + 4b2 =m2 - 8ab
       AC = 16, BD = 12 cm                                      from (i) and (ii)
       Thus, OA = 8 cm, OB = 6 cm                               m2 - 8ab = P2
       Thus, Diagonals of rhombus bisect each other at          8ab = m2 - P2
       90°                                                      4 × (2ab) = m2 - p2
       In right Δ OAB                                                        (m2 - p2)
       AB2 = OA2 + OB2                                          Area of Rhombus
                      D               E                                 B                  C
                                                                    Thus, OB = OD = 16 and OA = OC = 12
                  3                                                 (Diaggonals of Rhombus bisect each other at 90°)
                                                                    In Δ OBC,
                                                                    BC2 = OB2 + OC2 = 162 + 122 = 400
                                                                    BC = √400 = 20 cm
              B                           C                         Perimeter = 20 1 4 = 80 cm
                                                             267.   (a)         D          4x         C
       Thus, DE || BC
       Thus, ∠ADE = ∠ABC and ∠AED ∠AEB
       Thus ΔADE - ΔABC
                  22/52 =                                                                                    2x
       Thus, Area DECB = Area(ABC) - area (ADE)
       = 25 – 4 = 21
       Thus,           =
                                                                       A         N                  4x       M    B
264.   (a)
                A                 B                                                                 7x
                                                                    area =
                                                                    11x2 = 176 → x2 = 16
                                                                    x =4
           D                 C
                                                                    AB = 7 × 4 = 28 cm
       AB = BC = CD = DA = 10 cm
                                                                    CD = 4 × 4 = 16 cm
       BD = 16 cm
                                                                    CM = 2 × 4 = 8 cm
       In Δ ODC
                                                                    AM = AN + NM
       OD = 8, CD = 10, ∠DOC = 90°
                                                                    → AN + 16
       Thus, OC = √(CD2 - OD2) = √   2 - 82)
                                                                    → 6 + 16 = 22 (AN = BM =
       = 6 cm
       Thus, Now, Area of Rhombus ABCD = d1 × d2                    AC2 = CM2 + AM2
                                                                    AC2 = 82 + 222
                                  2
                                                                     AC = √               √                  √
265.   (a)                                                   268.   (c)
       Area if trapezium                                                             A
        =                =
                 2
        = 28 cm
266.   (a)
                       C                                                                  h
       ABCD is a rhombus
       AB = 6
       (Perimeter = 60 cm)                                       D                20 cm             C
       AC = 24                                                   As we know
       AP = 12                                                   → Area of trapezium
       [Diagnonals of rhombus bisect perpendicularly]            =
       In Δ APB                                                  → 175 =              ×h
       AB = 15, AP = 12
       Thus, BP = 9                                              → height = 10 cm
       (By pythagoras theorm)                             272.   (a) Let the rate of carpenting = Rs. x meter2
       Bd = 9 × 2 = 18                                           Thus, Length × breadth × x = Rs. 120 ……… (i)
       Area of rhombus                                           Length × breadth – 4 × x = Rs. 100 ………. (ii)
              Diagonal1 × diagonal2
       =
       → 216 sq cm                                               Breadth = 24 m
269.   (d) Let ABCD is || gm
       || Gm area of ABCD = 1 ÷ area of ADC               273.   (b) Area of Room = 100 × 3 = 300 m2
       Fro area of (ADC)                                         Carpet Length =
        A        30 cm       B
                                                          274.   (a) Old expenditure = 1000
                    40cm                                         Increase in area = 50 × 20 m2
           20cm                    20 cm                         Increase in expenditure = 50 × 20 × 25 = 250
                                                                 → New expenditure = 1000 + 250 = 1250
       D       20 cm           C                          275.   (d) Area of veramdhah =
                                                                 (25 + 3.5) × (15 + 3.5) – 25 × 15
       Let a = 20 cm, b = 30 cm, c = 40cm                        = 527.25 – 375 = 152.25 m2
       S=         =           = 45 cm                            cost of flooring = 152.25 × 27.5 = Rs. 4186.50
       area = ADC                                                (app.)
                                                          276.   (b) 2 πR1 = 528
       =√
                                                                 →2×         R1 = 528
       =√
                                                                 → R1 = 84 m
       =√
                                                                 → New Radius = R1 - K = R2
       = 75√15 cm2
                                                                 → R2 = 84 – 14 = 70
270.   (a)
                                                                 New Radius R2 = 84 – 14 = 70
       Let the diagonal of rhombus
                                                                 Area of Road = π(R12 - R22)
       d1 = x & d2 = 2x
                                                                  → π × 14(154)
       Area of rhombus = d1 d2                                   → Total expenditure
                                                                 →
                                                          277.   (b) Since the ratio of length and breadth = 3 : 2
                                                                 Let length of rectangular field = 3x
x y
* +
                                                                         ×
                              D
             A                            D                          ay : bx
                      2               3                       284.   (a) Ratio of parallel sides = 5 : 3
                          5                                          Let sides are 5x and 3x
       AB = 5cm                                                        (sum of parallel sides) × Perpendicular
       DB = 3cm                                                      distance = 1440 m2
       Thus, AD = 2 cm
                                  2
                  =
                                                                     4x × 24 = 1440
             2
                =                                                    x =
280.   (d) Base = Corresponding altitude                             Thus, Length of longer side = 5x
        = 3 :4                                                        = 5 × 15
       Let the base = 3x                                              = 75 m
       Altitude = 4x                                          285.   (c)
       Thus, Area of triangle = 1176
                    a1                       a2
                                                                      Let R = 23x , s = 22x
                                                                     Thus, R – r = 5
       a12 /a22 =
                                                                     23x – 22x = 5
                    √
         a1 /a2 =                                                    → r = 22 × 5 = 110
       Ratiio of their perimeters                                    Diameter of inner circle = 2r
                                                                     = 2 × 110
        = 4a1/4a2 = a1/a2 =
                                                                      = 220 m
       → 15 : 16                                              289.   (b)          a
286.   (d) Clearly, 3, 4, 5, from a triplet therefore,
       consider the triangle, a right triangle
       Let the sides are 3, 4, 5 triplet                                              a√2
       Perimeter = 3x + 4x + 5x = 12x                                        a                       a       a√2
       area of triangle =
                         = 216                                                             a
       x2 =
         x = √36 = 6                                                                 a√2
        thus, Perimeter = 12 × 6 = 72 cm                                                                 a√2
287.   (a)
                                          6x
       Perimeter of rectangle = circumference of circlare
       wire                                                              √
        2 (6x + 5x) = 2                                       290.
       22x = 2 × 22 × 6
        x = 12
       Clearly,
       Smaller side of rectangle = 5 × 12 = 60 cm                                    a           a
288.   (c)
                                                                      a          a                   a   a
                         5m
                                   r
                                       R                                                   a
                                                                                                 √
                                h1                                   h2             299.   (c)
                                                                                            Ratio of sides =
                                                                                           = 20 : 15 : 12
                                                                                           = 20 + 15 + 12 = 47
                                                                                           → 47 → 94
                                a1                              a2                         →1 →2
       √                                                                                   → Smallest side = 12 × 2 = 24 cm
                                                                                    300.   (a) Let the sides be = 3x, 4x, 5x, and 6x
       √                                                                                    → 18x → 72, x → 4
                                                                                           → Greatest side = 6 × 4 = 24 cm
                    √
                                                                                    301.   (b) Ratio of circumference = Ratio of radius
                    √                                                                       =3:4
                                                √           √
       Ratio of altitudes = *                       +                 ]             302.   (b)
                                                                                           Let the sides be = 2x, 3x and 4x
       =            =
                                                                                           → 9x = 18 = x = 12
293.   (d) Let length = 5x                                                                 → Sides are 4, 6 , and 8 cm respectively
       → Breadth =                                                                         Using hero’s formula
       Thus, Required ratio =                                                               S =
        =5:3                                                                                → Area = (√                               ]
294.   (c)                                                                                  =√                  ]
                                                                                                       2
                                                                                                √
                         o                                               = 4x2√20x2
                                                                        = 8x3√5 = 8√5
                                                                         = x3 = 1
              B              C                                            x=1
       As D and E are mid-points                                        Thus, 3rd side = 3 × 1 = 3 units
       → DE || BC                                                307.   (c) 3,4 and from treplet
       → Δ ODE – ΔBOC                                                   Let the sides be 3x, 4x = 72
       and also                                                         → 6x2 = 72
       (as D and E are mid-points)                                      → x2 = 12
                                                                         → x = 2√3
                                 ( )2 =
                                                                        Thus, Smallest side = 3 × 2√3 = 6√3
                                                                 308.   (b)
                                                                         Let the sides be 3x, 4x and 5x
       As D and E are mid-points
                                                                        → area =
       → DE || BC
       → Δ ODE - ΔBOC                                                   → 6x2 = 72
                                                                        x2= 12
       and also
                                                                        X = 2√3
       (as D and E are mid-points)                                      → Perimeter of equilateral Δ
       →          =( ) =¼                                                = 12 × 2√3 = 24 √ 3 units
305.                                                                                      √
                                                                        Side of Δ =                8√3 units
             A                            D                                           √
                                                                        Area of Δ =           × (8√3)2
                                                                             √
                                                                         =                      √
                 θ                            θ
                                                                 309.   (d) Let the parallel sides be 2x and 3x
                                                                        → Area =
                                                                        5x = 80
                             θ                                          x = 16
             B                     C      E              F              → Longer parallel side = 16 1 3 = 48 cm
                                                                 310.   (a)
       The given angle is same let verticle angle = θ                   Let the side of square = a
       (Thus,Δ ABC and ΔDEF are isoceleus triangles)                    Thus, Side of equilateral Δ = √2 a
       → When two angles are equal then third angle is
       also equal                                                                              √ √
       Thus, ΔABC – ΔDEF                                                Required ratio =
       ΔABC is similaer to Δ DEF
       Thus,                                                             =   √   ×2 = √3 : 2
             √                                                   311.   (b) Ratio of area = (Ratio of side)2
       →
             √
                                                                                          ( )            = 25 : 16
                                                                                    Required ratio =
                                                                                                                           ( )
                                                                                    =8:9
                                                                             317.   (c) 2(l + b) = 3a
312.                                                                                Thus, (a = side of equilateral traingle)
       (a)           =                                                              Let (b = a)
                                                                                    → 2(l + a) = 3a
                 =                                                                  2 (l + a) = 3a
                                                                                    2l + 2a = 3a
                 √                                                                  2l = a
                                 √
       = 2 : √7                                                                     Required ratiio =
                                                                                                               √             √
313.   (c)
              –                                       –
                                                                                    √
        =                                                                                   = 2 : √3
                                                                                    √
        → 16 : 25                                                            318.
                                                                                    (b) Required ratio =
314.   (a) Let side of square = a
                                                                             319.   (c) Let AB = 1, BC = 1
       radius of smaller circle =                                                                A       √2
                                                                                                                                 D
                                                  √
       Radius of larger circle =                                                             1
                         ( )
                                                                                        E                  1            √2       √2
       ratio =                           =
                         √
                     (       )
                                                                                                       B               1         C
315.   (c)                       A
                                                                                    Thus, AC =
                                                                                    √                      √
                                         a                                                                  √
                                 a
                                                                                                               √
                                         √3                                                                        √
                 B                                C                          320.
                                                                                    (b)                                ( )           ( )
       Circum radius =                                                       321.   (c) A
                                     √            √
       Equilateral Δ
                                     √
                                                          √
       Requird ratio =
                                     (        )
                                         √
       = 3√3 : 4π
316.   (d) 2(l + b) = 4a (a = side of square)
       2(2 + 1) = 4a
                                                                                        B        1         B       1         C
       2 × 3 = 4a
= 25 + 25 +
                                                                      10                        13
345.   (d) Radius 100 → 101
       Area 10000 π → 10201 π
       % increase =         × 100 = 2.01%                                      -3
                                                                  Other side will have to be decreased by
346.   (c) Let the breadth = x cm
       → Length = (x + 10) cm                                     →
       According to the question,
       x (x + 20) = (x + 10)(x + 5)                        352.   (c) Percentage increase in area
       → x2 + 20x = x2 + 15x + 50
                                                                   = 100 + 100 +
       → 5x = 50
       → x = 10                                                    = 300%
        → Area = 10 (10 + 20) = 300 m2                            Alternate :
347.   (c) Length 20 → 21                                         L       B               Area
          Breadth 50 → 49                                         1        1               1
          Area 1000 → 1029                                                                       +3
                                                                  2         2              4
       % error =                    × 100 = 2.9%
                                                                  Percentage increase = ×100 =300%
348.   (d) Length 10 → 13
          Breadth 10 → 12                                  353.   (d) x + y +
         Area    100 → 156
       % increase in area                                          = 10 – 10 +                 = - 1%
        =             ×100 =56%                                   (Negative sign shows decrease)
                                                           354.   (a) Let the side of cube = a
349.
       (d) 40% =
        Side       Surface area
        5            (5)2 = 25
       40%                     24
                        2
         7          (7) = 49
       % = Increase =
       Alternative:
       Percentage increase in surface are
       = 40 + 40 +     %
       Length of diagonal = 15 cm
                                                                     [1 m3 = 100 It
       √(l2 + b2 + h2) = = 15
                                                                     1000 cm3 = 1 It]
       (l2 + b2 + h2) = = 225 cm
       (l + b + h)2 - 2(lb + bh + hl) = 225                          h = m = 0.20 meter
       (24)2 - 2(lb + bh + hl) = 225                          395.   (d)
       576 – 225 = 2(lb + bh + hl)                                   Number of cubes =            =8
       Thus, Total surface area = 351 cm2
                                                              396.   (a) When we change shape of a solid figure,
                                                                     volume remains constant
                                                                      Volume of hemisphere = volume of cone
                                                                         R3 = π R3 h
                                                                     Thus, 2 R = h
                                                              397.   (d)
                                                                     According to the question,
                                                                     Let the radius of sphere = r cm
                                                                     4 π (r + 2)2 – 4πr2 = 352
                                                                     In such type of questions take help from the
                                                                     options to save your valuable time
391.   (c) Let length = 3x, breadth = 4x
                                                                     4π,(r + 2)2 - r2} = 352
       Height = 6x
                                                                     4π,r2 + 4 + 4r – r2} = 352
       3x × 4x × 6x = 576
                                                                     π (1 + r) =       = 22
       x3 =         =8
            3                                                        Take = r = 6
       x = √8 = 2cm
       Thus, Length = 3 × 2 = 6 cm
       breadth = 4 × 2 = 8 cm,                                        = 22
       height = 6 × 2 = 12 cm                                        Then option (d) is the right answer.
       Total surface area = 2 (lb + bh + hl)                  398.   (d)
                R = 32 cm
       We have to find the slant height                        H -h=
       Take ratio of H and R                                   =     cm
       = 60        :       32                           401.   (d)
         15        :        8
       L = √*(15)2 + 82 = 17
       = 17 × 4 = 68 cm                                                                     h = 40 cm
       Cost of painting = Surface area of cone × 35
       = π r L × 35
                       × 35
       = Rs. 23.94 (approx)
399.
                                                                Circumference of its base = 66 cm
                                                               2 π r = 66
                                                               r =
                                                               Thus, Volume = πr2h
                              H = 10 cm
       r = 2 cm
                                                                 = 13860 cm3
                                                        402.   (a)
[Spherical balls]
                     R = 20 cm
                  [Solid Cone]                                                          h
       Let the spherical balls made
       = ‘x’
       According to question,                                               r
       Volume of cone = x × volume of sphere
                                                                              r
            R2 H = x × π r3
                                                               According to question,
       (20)2 × 10 = x × 4 × (2)3                               2πr = 6π
       x = 125                                                 r = 3π
                                                               height of cylinder = diameter
                                                               = 2 ×r = 2 × 3 = 6 cm
                                                               Volume of water = π r2 h
                                                               = (3)2 × 6 = 54π cm3
                                                        403.   Volume of the cone = π (15)2 × 108 cm3
                                                               Volume of the cylinder = π × r2 × 9 cm3
                                                               According to the question,
       r2 =                =900
       r = √900 = 30                                           =
404.   (d) Volume of new sold sphere
        =        ( )        ( )       ( )
                                                        410.   (c) Volume of Sphere = Volume of displaced water
              π r3 =                        ]
         3
        r = 216, r = 6 cm
        Diameter of the new sphere = 2 × 6 = 12 cm            h =
405.   (d) Let the radius of new ball                   411.   (d)
        = R cm
       Then, πR3 =         π (33 + 43 + 53)
        R3 = 27 + 64 + 125 = 216
       R = ∛(6 × 6 × 6) = 6 cm
406.   (d) Volume of the new sphere
       = [r13 + r23 + r33]                                              r = 3cm        =
            R3
           [r13 + r23 + r33]
       R3 = r13 + r23 + r33                                                                     R = 6 cm
       R 3 = 13 + 63 + 83                                      Volume of cone = Volume of sphere
          = 1 + 216 + 512 = 729                                 π R2 h = πr3
       R = 729 = 9 cm                                             π×6×6×h = π ×3×3×3
407.   (b) 1 = 2.5 km
                                                                h =3
       Area of base = 1.54 km2
                                                        412.   (b) Volume of a cone = π r2h
       πr2 = 1.54
       r2 =                                                        π r2(24) = 1232 cm3
             √                                                 r2 =
       r =             =0.7 km
                                                               r2 = 7 × 7
       We know that, l = r2 + h2
                       2
                                                               r =         = 7 cm
       h2 = √(l2 – r2)                                         l = √r2 + h2 = √(72 + 242) = √625 = 25
       = √(     –                                              Curved surface area = πrl
       = √5.76 = 2.4 km                                        =                     cm2
408.                                                    413.   (d)
       (c) Radius =                          9.6 m
                                                               Volume of a sphere
       height = 2.8
       l2 = r2 + h2                                             =        (14)3
       =                                                       =          (14)3 ,      -
       1 = √100 = 10 m                                         Radius = 14
       Area of the canvas = πrl                                Curved surface area of sphere = 4π(radius)2
       =                                                        =4×    × 14 × 14 = 2464 cm2
409.   (c) External radius R = 4 cm                     414.   (b)
       Internal Radius = 3 cm
       Volume of iron used = πR2 h – πr2 h
       = πh (R2 + r2)
415. (a) 1 dm = 10 cm
                                                                                                           8 cm
       1m
                                                           r
                                = 21 cm
                                                                                  8 cm
       R = 15                                                                              12 cm
       Volume of well = volume of embankment                      12 cm = 4
       π(10)2 × 14 = π (152 - 102) × H
       H =          = 11.2 m
421.   (b)
                   R
                                                                  Thus, Cylinder is folded along the length of
                                                                  rectangle
                                                                   2 π R = 22
                                                r = 7 cm
                            H =                                   R =      =
                                                                  Volume of the cylinder = πR2 H
                                                                  = 22 × 7 × 3 = 462 cm3
       Volume of sphere = volume of cylinder               424.   (b)             R=                             r
           (7)3 = π (R)2 ×
       R2 = 4 × 7 × 7 = 2 × 2 × 7 × 7
       R = √(2 × 2 × 7 × 7) = 2 × 7 = 14 cm
       Diameter of base of cylinder = 2R = 2 × 14 = 28                                H = 8 cm
       cm                                                         h = 1800 cm
422.   (b)
                              R                        r                     (Rod)
                                                                  wire
                                                                  Volume of wire = Volume of Rod
                                                                  π r2 h = π R2 h
       ATQ      R + r = 10                                        r2 =
                (R + r)2 = 100
        2    2
       R + r + 2Rr = 100                                          r =√
       R2 + r2 + 100 + 2Rr     …… (i)
            3           3
         πR +          r = 880
        π (R3 + r3) = 880
       R3 + r3 =       =
       10 × (100 – 3Rr + Rr) = 210                         425.   (b)
                                                                                                      h
                                                                6 cm
       Volume of cylinder = 12 ×
       volume of sphere
        π (8)2 × 2 = 12 × πr3
       r3=
                                                                                           3 cm
        r =√              = 2 cm
       r = 2 cm
                                                                n =
       d = 4 cm
426.   (c) 2 π r - 2 π r = 5
       (R - r) =
427.   (c)
                                                         430.   (c) Height of cylinder = Breadth of tin foil
                      r                                         → Circumference of the base of cylinder
                                                                 = Length of the foil = 22 cm
                                                                → 2 π r = 22
                                                                r =                        cm
                                                                           = h2 + r2
                         R = 7 cm
                                                                                       h2 + 245
       Volume of bigger cone
       = × π (7)2 × 24                                          → h2
       =                                                        → h2 =
       = 22 × 7 × 8 = 1232 cm3                                             √
                                                                Volume = π r2h
                                    =
                                                                                   √       √          √
                                    =
                                                                = 616√5 cm2
                                         2
       Volume of smaller cone = 154 cm                   432.   In this case the breadth becomes the
       →
       → DE = 4.5 cm
                                                                                     2√3
                                                                     Slant height = √( √ )
445.   Height ofcylinder = Diameter of sphere
                                                                     = √
       →                                                      452.   (b) Volume of vessel = Volume of roof
                                                                      π × r2 × h = 22 × 20 × x
                                                                     (Where is rain in cm)
446.                                                                 → =
       (d)             =1
                                                                     → x = 2.5 cm
                                                              453.   (a)
                                                                     Volume of remaining solid
                                                                      = π r2h
                                                                                                    cm3
                                     3h = 2d                  454.   (c) Let the height be H3→
447.   (a)                                                              R3
       Volume of water pumped out in one hour
                                                                     → H =
        =                     ×12×3600
                                                              455.   (c) Let height and diameter be 3x and 2x
       = 1663200 cm3                                                 →     x3 × 3x = 1078
       = 1663.2 ltr.
448.   (d) 2 π rh = 1056                                             → x3               =49×7
       r =                                                           →x =7
                                                                     → Height = 7 × 3 = 21 cm
       Volume = π r2h =                        ×16            456.   (c) Radius of cylinder r = 10 cm
       = 5544 cm   3                                                 height of cylinder h = 2 cm
449.                                                                 Volume of cylinder = πr2h
       (b) π r2 H =           r2 h
                                                                     radius of cone → radius of cylinder = 10 cm
       H =                                                           Let height of cone = h1
457.   (a)                                                    .
                            6 cm
6 cm
24
r r
                                                                                  r1
                                                                The circumference of base of cone
                                                              → Circumference of sheet
                                                              2 π r1 = 14 π
                                                              r1 = 7 cm
                                                               radius of cone = 7 cm
                                                              Slant height = radius of semi-circular sheet
                                                               r = 14 cm
 Height = √ –
=√ = 12 cm (approx)
462.
(b)
461.   (b)
                                                                               r                r
                                            r
                r         r                                                                r1
                      r            →
                                       r1         r
4 cm
3 cm
                                                                         (             )
                                                                  → 2 × 27π = 54π cm2
                                                           477.   (c)
472.   (c)
       Radius of base =         =                                                  ----------
                                                                                   - -- - - - - - - -
490. (d) r
r 493. (c)
       2 πr = a,
       r =
       Volume of cylinder = V
                                                                                           h1              h2
       π r2h = V
       π(     )2 ×h = V
               ×h =V                                                                            r1              r2.
        h =                                                                                =         =
491.   (d) Radius of sphere =
       Let the height of the cylinder = h                             ( ) ×            =
       ATQ
       Volume and radius are same                                     Thus,
       π (6)2 ×h =     (6)3
                                                                      ( )          =
       h =         = 8 cm
492.   (b)
                                                                            =
                                h = 21 cm
                                                               494.   (d)
       Perimeter of base = 8 cm
                                                                                  h
       2πr =8
                                                                      2m
= ( ) =( ) =
       = 9 : 16
496.   (c) Ratio of surface area of sphere
                                                                                          h                  H
                    =
        (       )
                                                                           Volume of water in conical flask =      π r2 h
                                                                           If the height of water level in cylindrical flask = H
       Ratio of their volume                                               units
                                                                           Thus, π m2 H = π r2h
                    ( )           =(   )
                                                                            H =
       = 8 : 27                                                     499.   (d)                                   R = 7 cm
497.
                                                             r
                        28
                                                                           Volume of the solid sphere
       7×7×h=              ×7×7×7
                                                         503.   (d)             r = 50 cm
       h =       cm
500.   (b)
                                                                               h                =6×        r = 50
                           r=3
                                                    H
                                                                Volume of cylinder
                                           R
                                                                = 6 × volume of a sphere
       Volume of sphere = = π r3                                π 502h = 6 × π 503
       = π × 3 × 3 × 3 = 36 π cm3                               h =6×
       If the water level rises by H cm                          = 400 cm
         π R2 H = 36 π                                          =4m
       6 × 6 × h = 36                                    504.   (b)
        h =1
501.   (b)
                                                                                   h        +          h   =
                            R=9                 4               5 cm
       Volume of sphere = π R3
                                                                Volume of both the cones will be equal to the
        = 972 π cm3                                             volume of sphere
       Let the length of wire = h cm
                                                                 π32 h + π42h = π53
       π (0.2)2 ×h = 972 π
       h =                    cm                                 h 3 2 + 42 = × 5 × 5 × 5
       = 243 meters                                                    × 25 = × 5 × 5 ×5
502.   (a) Volume of sphere = Volume of rectangular             h =    × 3 = 20 cm
       block
                                                         505.   (a) Volume of cone = πr2h
                       3
           π (radius) = Length × Breadth × height
                                                                Now, r1 = 2r, h1
           π (radius)3 = 21 × 77 × 24                           = 2h
                                                                Thus, Volume of second cone
h l
                                  r                         510.   (c)
       C = π rl
       C2 = πr2r2l2
       V = π r2h
       V3 = π2r4h2
       3 πvh3 - c2h2 + 9v                                                              3.6 cm        h          h
       3π × π r2h           h3 - π2r2l2h2 + 9 × π2 r4 h2
       = π2r2h4 - π2r2h2 (r2 + h2) + π2r4h2
       = π2r2h4 - π2r4h2 – π2r2h4 + π2r4h2 = 0                                         1.6 cm                   1.2
507.   (a) Volume of rectangular block = 11 ×10 × 5                cm
       = 550 m3
       = 550000 dm3 (1 m = 10 dm)                                  According to question,
       Volume of a sphere
                                                                    × π × 1.6 × 1.6 × 3.6
        π×             dm3
                                                                   →
       =      dm3
                                                                    h =
       ATQ      n×      = 550000
       n =            = 8800                                       =      6.4 cm
508.   (a) Required number of spheres                       511.   (a)
                                                                                                         × 32
                                                                            (      )
                                                                   = 4×π×9 =           =36π units
                                 = 81
                                                            512.   (d) Radius of sphere =       cm
509.
       (d)                                                         Volume of a sphere = π ×
                                                                   Let the radius of cone = R
π× ×32000 ( )
R3 =
       R=                                                          But, h2 = 30
       Height of glass = 2R × 2 × 2 = 4 cm                          3 = 30 cm
513.   Volume of earth taken out = 40 × 30 × 12 = 14400            1 = 10 cm→ h1 = 10
       m3                                                          height from base = 30 – 10 = 20 cm
       Area of rectangular field = 1000 × 30 = 30000 m2
       Area of region of tank = 40 × 30 = 1200 m2
       Remaining area = 30000 – 1200 = 28800 m2
       Increase in height =
       = 0.5 m
514.   (a)
       R = 6 cm
r r
H = 12 cm
       According to question,
       8 × π r3 = π (6)2× 12                                516.   (d)
       r3 =
        =3×3×3
       r = ∛(3 × 3 × 3) = 3 cm
515.                                                               .                      r
                                                                                     R
                              h1
                                      Height = 30 cm
                                          h2
                                                                   Volume of lead = π r3
                                                                   Volume of Gold = π r3 -        r3
                                                                   According to question,
                                  R
                                                                    π R3 – π r3 = π r3
                                                                       π R3 = π r3
                                                                       r3 = 2 r3
                      7
                                 7                                h =          =3 cm
                          7                                521.   (d)
                                                                  Number of bottle
                                                                  =
                  r                                               V1 =              =
                                                                               2
                      R                                    523.   4 π (Side)       = 346.5
                                                                  (Side)2 =                  = 5.25 cm
              =√
       Squaring both sides
          =
         =         +
528.   (c) Diagonal of cube will be equal to diameter of
       sphere
        √3a = 2 × r
                             C
       Δ ABC = equilateral Δ                                           (Multiply 4π both in Numberator & denominator)
        ACB = 60°
                                                                                            =
           BCP = 30°
       ΔCDO, LDO = 90° (Angle b/w radius and tangent
       is 90)                                                   535.   (a) According to the question,
       OD = 1P = 1 cm                                                  Volume of sphere = π r3
       OC = 2P = 2(1) = 2 cm                                           Volume of cylinder = π r2h
       then, CZ = OC + OZ
       = 2 + 1 = 3 cm                                                    r=h =          = 4 cm
       Δ CZY CZY = 90 °
                                                                       C.S.A of cylinder = 2 π rh
       CZ = √3P = 3 cm
       YZ = 1P = √3 cm                                                 =2×          ×3×4
       Now, In cone XYC
       r = ZY = 3 cm                                                   =                         =     cm2
       h = CZ = 3 cm                                            536.   According to question,
       Vol. cone = π r2h = π (√3)2 (3)                                 R = 6 cm
       = 3 π cm2                                                       → The capacity of the hemispherical bowl
       Vol. of sphere = π r s3                                         = π r3 = ×               × 63
r = 2.1 cm
20 cm
                                                                  r = 2.1 dm
                                                                  h = 4.2 dm
                                                                  (for max)
       According to the question,
                                                                  Volume of cone =      π r2h
       → r = 7 cm
       → h = 20 cm                                                 =        × 2.1 × 2.1 × 4.2
       → Total surface Area of cylinder = curved surface          = 19.404 dm3
       Area + 2 × area of base                             541.   (d) Let the initial radius = r
       2 π rh + 2 πr2                                             According to the question,
       = 2πr (r + h)                                              4π(r + 2)2 - 4πr2 = 352
                                                                  r2 + 4 + 4r – r2 =
       = 44 × 27
                                                                  4r + 4 = 28
       → TSA of cylinder = 1188 cm2
                                                                   r =6
538.   (d) According to question,
                                                           542.   (a)
       Given,
       → Radius of cylinder
        =r
       → CSA of cylinder = 4 π r h
       → As we know
                                                                                         9                 15
       → Curved surface area of cylinder
       =2πRH
→ ×x =1
                                                                     x =
                                                                     = 1 hours 10 minutes
                                                              548.   (a) Diameter = 5 mm = 0.5 cm
                                                                     radius = 0.25 cm
                                                                     Volume of water flowing from the pipe in 1 minute
                                                                     = π × 0.25 × 0.25 × 1000 m3
                                                                     Volume of conical vessel = π × 15 × 15 × 24 cm3
                                                                     Thus, Time =
544.   (c) Radius of 1st. solid metallic spheres = R = 6 cm          =
       Radius of 2nd. solid metallic spheres = r = 1 cm
                                                                      = 28 minutes 48 seconds
       Internal Radius of hollow spheres= x
                                                              549.   (d) r = 12 m, h = 9 m
       External Radius of hollow sphere = x + 1
                                                                     l = √
       So, π (R3 + r3) = π *(x + 1)3 – x3]
                                                                       =√            = 15 m
       216 + 1 = x3 + 1 + 3x (x + 1) – x3                            Cost of canvas = curved surface area = × cost of 1
       216 = 3x (x + 1)                                              m2
       72 = x2 + x                                                   Rs. 67824
        → x2 + x – 72                                         550.   (d)
        =0
       After solving,
       x = 8 cm                                                                                      0.1 cm
       So, the external radius of the hollow sphere
       = x + 1 = 8 + 1 = 9 cm
545.   (a) Let the time taken to fill the tank = x hrs                                           x
       → (π r2 h) × x = 50 × 44 ×
                                                                     8.4 gm = 1 cm3
       →x=
                                                                      4725 gm =         cm3
       = 2 hrs
                                                                     Volume = x × x × 0.1
546.   (b) → The area of ground
                          =1
                                                                                                       ( )
                                                                    ( )                 ( )       =
       ( )     =
                                                             556.   (d) 2 πr h = 264 …. (i)
                                                                    π r2h = 924 ……… (ii)
               √
                                                                    On diving =
           √                                                        r                  = 7 cm
       =
                                                                    Diameter = 2r = 2 × 7 = 14 cm
       Thus, Ratio of their ratio
                                                                    putting, r = 7 in (i)
       = √2 : 1
                                                                    2π r h = 264
                                                                    h =                        = 6 cm
                                                                    Required ratio =
553.   (a) We are given that volume of two cube are in
       the ratio= 27 : 1                                                =
                                                             557.
       ( )
                                                                    (b)                           =
                   3
                       √
                                                                                       =
                                                                              =
554.   (a)
       Ratio of edges of cuboid = 1 : 2 : 3                  558.
                                                                    (c)                    =
        Let, l = x , b = 2x, h = 3x
       Surface area = 88 cm2                                            ( )        =
       2 (lb + bh + hl) = 88
       2 (2x2 + 6x2 + 3x2) = 88                                     Ratio of their total surface area
       11x2 = 44
       x2 = 4                                                           =          =       ( )
       x =2
        Thus, l = 2 cm, b = 4 cm,                                   =       ( )        =
       h = 6 cm                                                         = 9 : 16
                        √
                    =
             √
        = √2 : 1
560.   (c) Let height of cone = h                                                                                   1
       radius of cone = r                                                              5
       Volume of cone = π r2h
        Now height is doubled                                       Ratio of total surface area
                                  2
       Volume of new cone =         (2h) = π r2 h                    =
       Required ratio = 1 : 2                                        → 1 : 25
561.   (d)                                                   564.
                                                                    (b) Let r1 =       cm
                            r1 = 40 cm                r2 =          r2=         cm
       10 cm                                                        Required ratio =
                                                                           =
                               A
       B                                                                               =
                                                                    = 36 : 25
                                          =   ( )            565.
       ( )          → 16 : 1                                                         6 cm
                                                                                              =                +
562.   (d)                                                          +
                                                                                                      3x
                                h1                                  4x                  5x
       h2                                                             π ,(3x)3 + (4x)3 + (5x)3 = π (6)3
                                                                    x3 (27 + 64 + 125) = 216
                                                                    x3 - × 216 = 216
                                     r1                             x3 =      =1
                                                                         3
       2r1                                                           x = √1 = 1
       R2 = 2r                                                      Radius of smallest sphere = 3x = 3 × 1 = 3 cm
       h 2 = h1                                                     x3 × 216 = 216
                                                                    x3 =        =1
                                                                            H= r
             B                                       C
                                                                            R=
                                   =            =     + =
       Area of part (ABCD) (i.e. frustrum) = 8 – 1                          2r (diameter ) × 2h = h
       Required ratio = 1 : 7
567.   (a)
                                                                     571.   (a) In this case height of cylinder and cone is equal
                                                                            to the radius od hemisphere
                                                                             H= r
        √                                                                   Ratio of volumes
                                                                     574.
                                                                                  =
568. (b) R
                                                      H = 2R                X=
                               R
                                                                     575.
                                                                            (c)       R
       (Height of cylinder = 2 × R)
                                       =
 ( )
       =
                                                                                   =3 : 2
       =
                                                         593.                                (√ )       √
                                                                (b) Ratio of volume =
                                                                                            (√ )       √
                                                                                        = √             √
       
                                                         594.                          √
        l2 = 25 √                                              (c) Side of cube             = 6 cm
                                                                                       √
        h2 = 16
                                                                Required rate                = 1    :       1
        √               = 25
        √                = 25                            595.   (d) Let the radius of hemisphere and sphere be ‘r’
                r=3                                             and ‘R’
       radius : height                                          
          3     :     4
587.   (b) Let the sides of the rectangular box he
         x, 2x, 3x
        2(2x2+6x2+3x2) = 88                                               √
        11x2 = 44                                               Ratio of curved surface area
               x2 = 4
                                                                =
               x=2                                                                    (√ )
        Sides are 2, 4, 6 cm                            596.
       Volume = 2×4×6 = 48 cm3                                  (b)
588.   (b) Ratio of volume =                                               r2                  r2
           √        √       √
           (√ )     √       √                                                                           h
            √       √                                                      h    h
589.
       (a) Ratio of volume =
                                                                    n=              = 8800
       volume remains same                                   601.
                                                                    (a)
       volume of sphere
       = volume of cone
       4r = h
                =4 : 1
598.   (c)                                                          ( )          ( )
       Let the side of first cube = a1
       and the side of second cube = a2                             ( )
                √
       Ratio of their surface area                                  =      8 : 3
       =                              = 9 : 16
599.   (a)
                                                             602.   (d)
                      r1             r2
                                                                                    R
       Ratio of volume of sphere
       x ratio of weight per 1 cc. of material of                                                     R/2
       each
       = Ratio of weight of two sphere
        8 : 17                                                     =       ( )
600.   (a)
       volume of rectangular block                                  =
       (    )            (       )
                                                                      606.   (a)
       1 :
604.   (c)                   A                                               volume of cone =
                                         h1                                  =                            cm3
                     B               C                                       Volume of cubical block = 10×5×2 cm3 = 100 cm3
                                                  h2                         Wastage of wood
                                                                                 (          ) cm3
                 D                            E
                     Cone                                                    =(           )          cm3
610.   (d)
                                                                             614.   (d)
                   r = 15 cm                      h = 15 cm
                                                                                    Let old radius = r
                                                                                     volume =
                                                  R = 15 cm
                                                                                    New radius = 2r
       Volume of cone
                                                                                     New volume =
       Volume of sphere                                                                              =
                                                                                     volume becomes eight times.
       Percentage wanted                                                     615.   (b) Radius 2 → 1
                                                                                        Height 5 → 8
                                           ×100                                         Volume 20 → 8
Volume of cone =
= (8)2×16
                        =
       Required percentage
= ×100
                        = 87.5%
620.   (a)                                                   623.   Let the initial radius = 1 unit
       Decrease in these radius                                     New radius = 2 unit (radius is
                                                                    doubled)
       = (decrease in base area)1/2 = (   )                         Radius :        Volume
                                                                                       (1)3
                                  =
                                                                                       (2)3
       Let initial radius and height be 3r and h
       New radius and height are r and 6h                           (       is constant)
       Old lateral surface area                                         1               1
        = 2 × π × 3r × h                                                                      7
                                                                                                 40 cm
                                                                                       area of base = 40×40
631. (d) A
                          a       a
                              a
                   B              C
       r – in radius of in circle of triangle
       perimeter = 15 cm (given)
       Semi-perimeter (S) =
       In radius of any triangle
                                                               633.   (c)
       r                                                                              a
                   a ea
       r=
       where Δ is the area of triangle
       r = 3 cm given
                    16                                                     637.   (b)
       Perimeter of the base = 4×16 = 64 cm                                                           √
                                                                                  volume of prism =        a2 × h
       # Curved or lateral surface area of pyramid
                                                                                                     √
       = × (perimeter of base) × height                                                          =        × (8)2 × 10
                                                                                                 = 160√ cm3
                                                                           638.   (b)
                                                        1                         Volume of prism
                                                                                   ×10×12×20 = 1200 cm3
                                                  8cm       8 cm
                                                                                   Weight of prism = 1200×6 = 7200 gm
                                                        16 cm
                                                                                                             = 7.2 kg
                                                                                           6 cm
                                r       r                                      Volume of prism = area of base × height
                                    r                                              √
                                                                               =         (6)2 × height
                   B                              C
       In radius of triangle                                                   √
                                                                                       × 6 × 6 height = 81√
                  =                                                                               √
                              pe imete                                         height =                       = 9 cm
       ar (Δ ABC) = Inradius × semi-perimeter                                                 √
        = 4× = 4×14 = 56 cm
       Volume of the prism = 366 cm3
       (area of base)× height = 366 cm3
       56 × height = 366 cm                                             644.   (d)
       height =       = 6.535 cm
                                                                                        10√                                12       slant height
642.   (d)                A                                                                                                     5
                              10√
                  √   O                 M M                                    Side of square =                     √ = 10 cm
                                                                                                          √
                                                  slant height
                                            (h)                                slant height = √                        = 13 cm
                         E
                                                                               lateral surface area = ×perimeter of base × slant
              B      10√        C O                       E
                     A        9 cm B
       In Δ ABD,                                                          Area of base = 10×10 = 100 cm2
       BD = √AB     AD = √                                                Area of 4 phase
       =√          =√    = 15 cm                                             = × Base × slant height) × 4
       Area of Δ ABD = × AB × AD                                                × 10×13×4
                                     2
       = × 9 × 12 = 54 cm                                                      = 65×4 = 260
       In Δ BCD                                                           [slant height = √             =√     = 13]
       semi-perimeter =                                                   Total Surface area
                                                                           260+100
       = = 21                                                              360 m2
       Area of Δ BCD =                                             658.   (d)
       √                                                                  volume of prism = (area of base × height)
       =√                                                                 Area of base (i.e. area of triangle)
       =√                = 21×4 = 84 cm2                                   Area of base
                                                                          =
       area ABCD = 84+54 = 138 cm2
                                                                           Area of base
       height of prism =
                                                                          =√
                                          = 15 cm                         = (By Hero’s formula)
                    ase
       perimeter of base =
                                                                          So, S =                    = 27
       9+14+13+12 = 48 cm
       Area of lateral surface = perimeter × height                        = 27
                           = 48 × 15 = 720 cm2                            √        (   –   )
654.   (a) As we know,
       volume of Right Prism = Area of the base × Height                  √
                     √                                                    √
        7200 =               P2 ×        √                                9×7×2
                          2
        72×2 = 9 P                                                       Volume of Prism
        P2 = 16                                                          =(9×7×2)×9 = 1134 cm3
       P=4
655.   (b)                                                         659.   (d)
       Half of its lateral edges                                          Let the side of the square = a cm
        Half of its edges                                                ATQ
        Half of its volume                                               T.S.A = C.S.A + 2 base area
       Then, volume reduced by = 50 %                                     C.S.A = base perimeter × h
656.   (b)                                                                T.S.A = base perimeter × h + 2 base area
       Total surface area                                                 192 = 4a × 10 + 2a2
            √                                                             2a2 + 40a – 192 = 0
       = 4×*             +
                                                                          a2 + 20a – 96 = 0
                2
       = √ cm                                                             a2 + 24a – 4a – 96 = 0
657.   (a)                                                                a(a+24)–4(a+24) = 0
                                                                          (a+24)(a–4) = 0
                                                                          a = 4, (–24)
                                                                          a = 4 (side can never be in –ve)
                               10
                                                                          Volume = base area × h
                         10          10
                   3x
       Base of prism
                                                         667.   (d) According to the question
        length : breadth
                                                                Volume of cylinder = Volume of cone
              3x : 2x
       Perimeter of base
       = 2(3x + 2x) = 10x
       area of base
        2x × 3x = 6x2
       height of Prism = 12 cm (given)
       total surface area of prism
       = Perimeter of base × height + 2 × area of base
       288 = 10x × 12 +12 x2                             668.   (d) According to the question C.S.A of cylinder
       12x2 + 120x – 288 = 0                                     = 2 πrh = 2 π 2
       x2 + 10x – 24 = 0                                        C.S.A of sphere = 4 π
       x=2                                                      2π =4π
       area of base  6×4                                               √
                      24 cm2
       volume of prism
        24×12
        288 cm3
                                                                    √
663.   (b)                                                      =
                                                                             √
       Volume of the part (prism) =                      669.   (a) Total surface area of prism
       Area of base × height
                                                                = perimeter of Base × Height
       Area of base (Isosceles Δ)                               + 2 × Base Area
       = √                                                      10 = 4a × 2 + 2 × a2
                                                                10 = 8a + 2 a2
       =       (1)2h = πh
       New radius of wire =   cm
       volume of new cone
       =     ( )
       H = 9h
       Height of new cone is increased by 9 times.
       [Slant height = √( )
       =√
       = 13 cm
673.   (a) By option (a)
       Are Increment = 20+20+
       = 44%