Gen Math WK 3-4
Gen Math WK 3-4
GENERAL
 MATHEMATICS
 Guided Learning Activity Kit
     Simple and General Annuity
         Quarter 2 - Week 3 - 4
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            SIMPLE AND GENERAL
                 ANNUITY
Introduction
Learning Competencies
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             Objectives
At the end of this learning activity kit, the students are expected to:
      1. describe simple annuity and general annuity;
      2. differentiate simple annuity and general annuity;
      3. solve for the future value and present value of simple annuities and
         general annuities;
      4. find the fair market value of a cash flow stream that includes
         annuity; and
      5. calculate the present value and period of deferral of a deferred
         annuity.
Review
2|P age
            3.   What is the present value of Php 80,000 after 2 years if money
                 earns 6% compounded monthly?
                   Given:       F=
                                im =
                                j=
                                n=
                   Find:        P=
                                                              im
                   Formula:     P = F ( 1 + j )-n where j =        and n = mt
                                                               m
Discussion
What is Annuity?
                                                                       3|P age
     This learning activity kit will focus on Simple Annuities and General
Annuities, Ordinary Annuities and Annuity Certain.
      For the purpose of our discussions, we will define terms that we are
going to use throughout our lesson.
Definition of terms:
4|P age
       Let us illustrate the cash flow in a table.
                       Amount of Savings in
 Time (month)                                         Amount in Pesos
                         Exponential Form
       1          10,000( 1 + 0.0075)5                  Php   10,380.67
       2          10,000( 1 + 0.0075)4                  Php   10,303.39
       3          10,000( 1 + 0.0075)3                  Php   10,226.69
       4          10,000( 1 + 0.0075)2                  Php   10,150.56
       5          10,000( 1 + 0.0075)                   Php   10,075.00
       6          10,000                                Php   10,000.00
           Total amount after 6 months                  Php   61,136.31
So, at the end of 6 months, you will have a total of Php 61, 136.31.
                       ( 𝟏 + 𝐣 )𝐧 − 𝟏
             F =   R
                             𝐣
                         ( 1 + j )n − 1
     Formula:      F = R
                               j
                                                                    5|P age
                                          ( 1 + 0.0075 )6 − 1
                   F = Php 10,000
                                                0.0075
F = Php 61,136.31
      Find:        F=?
                            ( 1 + j )n − 1
      Formula:     F = R
                                    j
                                        ( 1 + 0.0025 )144 − 1
                   F = Php 2000
                                               0.0025
F = Php 346,148.51
      Example 3. Bobet and Lyn are best friends. After graduating and
being able to get a decent job, they plan for their retirement. Bobet, starting
at age 24, deposits Php 12,000 at the end of each year for 36 years, while
Lyn, who started later at age 42, deposits Php 24,000 at the end of each year
for 18 years. Who will have the greater savings if both annuities earn 9% per
year compounded annually?
Solution:
Given:
      For Bobet’s plan                   For Lyn’s plan
            R = Php 12,000                     R = Php 24,000
             i = 9% =0.09                       i = 9% = 0.09
            m = 1 (annually)                   m = 1 (annually)
                 i    0.09                          i    0.09
             j=     =      = 0.09               j=     =      = 0.09
                  m    1                             m    1
            t = 36 years                       t = 18 years
            n = 36                             n = 18
6|P age
      Find: F = ?                           Find: F = ?
Formula:
           ( 1 + j )n − 1                                 ( 1 + j )n − 1
F = R                                            F = R
                 j                                              j
                     (1 +   0.09 )36   −1                           ( 1 + 0.09 )18 − 1
F = Php 12,000                                   F = Php 24,000
                            0.09                                          0.09
      Hence, at the end of the period, Bobet has Php 2,833,496,67 on his
retirement while Lyn has Php 999,232.11 so Bobet has the greater savings.
      Notice how the example shows the difference in their savings, so that
the value of time and the advantage of saving early affects the amount of
money.
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     Let us illustrate the discounted payments in a table.
     The present value of a Simple Ordinary Annuity can be found using the
formula:
                     𝟏 − ( 𝟏 + 𝐣 )−𝐧
           P = R
                            𝐣
                                      1− ( 1 + 0.0075 )−6
                 P = Php 10,000
                                            0.0075
P = Php 58,455.97
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     Example 5. Jason paid Php 300,000 as down payment for his car. The
remaining balance is to be paid in installment at Php 17,500 at the end of
each month for 5 years. If the interest is 10.2% annually compounded
monthly, what is the cash price of his car?
     Given:       down payment = Php 300,000
                  R = Php 17,500
                  i12 = 10.2% = 0.102
                  m = 12 (compounded monthly or 12 times a year)
                       i12 0.102
                   j=      =     = 0.0085
                        m     12
                   t = 5 years
                  n = mt = 12(5) = 60
     Find:        P=?
                        1 − ( 1 + j )−n
     Formula:    P = R
                                j
                                    1− ( 1 + 0.0085 )−60
                 P = Php 17,500
                                           0.0085
P = Php 819,841.61
                 t = 2 years
                 n = mt = 12(2) = 24
Find: P=?
                                                                     9|P age
                            1 − ( 1 + j )−n
        Formula:   P = R
                                   j
                                       1− ( 1 + 0.005 )−24
                   P = Php 2,500
                                              0.005
P = Php 56,407.17
                            1 − ( 1 + j )−n
        Formula:   P = R
                                   j
                                       1− ( 1 + 0.0075 )−12
                   P = Php 4,000
                                              0.0075
P = Php 45,739.65
      Therefore, buying the living room set in cash is lower than the present
value in its installment term.
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      Find:       R=?
                           1 − ( 1 + j )−n
      Formula:    P = R
                                  j
                                          1 − ( 1 + j )−n
                  Php 200,000 = R     [                    ]
                                                  j
                                          1− ( 1 + 0.005 )−36
                  Php 200,000 = R     [                         ]
                                                0.005
                  Php 200,000
                                = R
                  32.87101624
Php 6,084.38 = R
Thus, George must pay Php 6,084.38 every month for 3 years.
      However, not all annuities are simple ordinary annuities. There are
annuities where the length of the payment interval is not the same as the
length of the interest compounding period. Such annuities are called General
Annuities. General Ordinary Annuity is an annuity where the length of the
payment interval is not the same as the length of the interest compounding
period and is made at the end of the payment interval.
     For General Ordinary Annuity, you can use the formula for finding the
Future Value and the Present Value as follows:
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Amount (Future Value) of a General Ordinary Annuity:
                           ( 𝟏 + 𝐣 )𝐧 − 𝟏
               F =     R
                                 𝐣
                           𝟏 − ( 𝟏 + 𝐣 )−𝐧
               P =     R
                                  𝐣
       Note that the formulas are the same for a simple ordinary annuity. The
difference will only lie in finding the value of j: the given interest rate per
period must be converted to an equivalent rate per payment interval.
Note that the payment period is different from the interest rate period.
Steps:
      1. Convert 4.5% compounded quarterly to its equivalent interest rate
for monthly payment interval.
12 | P a g e
                             im mt
      Recall: F = P ( 1 +      )
                             m
      Let:
                            i12 12t                             i4 4t
             F1 = P ( 1 +      )                 F2 = P ( 1 +     )
                            12                                  4
                   F1 = F2
                 i12                     i4 4t
        P(1+        )12t
                         = P(1+            )
                 12                      4
                 i12 12               0.045 4
          (1+       )      = (1+           )
                 12                    4
                 i12 12
          (1+          )   = ( 1.01125 )4
                 12
                   i12
               1+      = [(1.01125)4]1/12
                   12
                   i12
                       = ( 1.01125 )1/3 – 1
                   12
                   i12
                       = 0.0037360247 = j
                   12
      Thus, the interest rate per monthly payment interval is 0.0037360247
or 0.37360247%.
F = Php 512,119.30
      Therefore, at the end of the period, Jericho will have Php 512,119.30 in
his account.
      Note. When solving for the equivalent rate j, use seven or more decimal
places or the exact value.
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        Given:           R = Php 15,000
                          t = 20 years
                         n = 2(20) = 40 payments
                       i(12) = 0.03
                         m = 12 (compounded monthly)
Steps:
      1. Convert 3% compounded monthly to its equivalent interest rate for
semi-annually payment interval.
                                  im mt
        Recall: F = P ( 1 +         )
                                  m
        Let:
                                 i2 2t                             i12 12t
                 F1 = P ( 1 +      )                F2 = P ( 1 +      )
                                 2                                 12
                       F1 = F2
                     i2 2t                i12 12t
           P(1+         )    = P(1+          )
                     2                    12
                      i2 2            0.03 12
               (1+      ) = (1+           )
                     2                 12
                     i2 2
               (1+      )    = ( 1.0025 )12
                     2
                       i2
                  1+         = [(1.0025)12]1/2
                       12
                        i2
                             = ( 1.0025 )6 – 1
                        2
                        i2
                    = 0.015094063 = j
                 2
     Thus, the interest rate per semi-annual             payment      interval is
0.015094063 or 1.5094063%.
F = Php 815,640.22
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Present Value of a General Ordinary Annuity
                        F1 = F2
                   i2                     i4 4t
        P(1+            )2t = P ( 1 +       )
                   2                      4
                   i2 2               0.10 4
             (1+     )       = (1+        )
                   2                   4
                   i2 2
             (1+        ) = ( 1.025 )4
                   2
                    i2
               1+            = [(1.025)4]1/2
                        2
                        i2
                     = ( 1.025 )2 – 1
                   2
                  i2
                     = 0.050625 = j
                  2
      Thus, the interest rate per semi-annual payment interval is 0.050625
or 5.0625%.
                                                                         15 | P a g e
                                                1 − (1 + 0.050625 )−8
                      P = Php 25,000
                                                     0.050625
P = Php 161,172.87
                         F1 = F2
                     i12 12t               i4 4t
           P(1+          )     = P(1+        )
                     12                    4
                      i12 12           0.09 4
               (1+      )      = (1+       )
                     12                 4
                     i12 12
               (1+       )     = ( 1.0225 )4
                     12
                       i12
                 1+   = [(1.0225)4]1/12
                  12
                  i12
                      = ( 1.0225 )1/3 – 1
                   12
                  i12
                      = 0.007444443 = j
                  12
      Thus, the interest rate per monthly payment interval is 0.007444443
or 0.7444443%.
16 | P a g e
      2. Apply the formula in finding the present value of an ordinary annuity
using the computed equivalent rate j.
                            1 − ( 1 + j )−n
      Formula:    P = R
                                    j
                                        1 − (1 + 0.007444443 )−12
                  P = Php 20,000
                                              0.007444443
P = Php 228,779.12
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      2. Find the periodic deposit R of an ordinary annuity using the
equivalent rate j.
                     ( 1 + j )n − 1
            F = R
                           j
                                    ( 1 + 0.0182446 )16 − 1
            Php 600,000 = R [                               ]
                                          0.0182446
            Php 600,000 = R ( 18.387310085 )
              Php 600,000
                             = R
             18.387310085
            Php 32,631.20 = R
Solution: Find the fair market value for each offer. Choose a focal date or
the date the term starts then determine the present values of the two offers
at that focal date. Assume that focal date is the start of the contract.
      Since the initial offer of Php100,000 is on the focal date, then its
present value is still the same as Php100,000.
18 | P a g e
For the First offer:
       For the present value of the Php 2,000,000 offered 5 years from now,
recall the formula:
       P = F ( 1 + j )-n     where F = future value
                                            im
                                        j =
                                            m
                                       n = mt
                                       P = present value
       Given:        F = Php 2,000,000
                     t = 5 years
                     m=4
                     n = 20 payments
                         i4    0.06
                     j=     =        = 0.015
                         4      4
       Find:         P=?
       Formula:      P = F ( 1 + j )-n
                     P = Php 2,000,000 ( 1 + 0.015 )-20
                     P = Php 1,484,940.84
      Since the payment interval is the same as the interest period, we will
use simple annuity.
      Solve for the present value of the simple annuity.
       Given:      R = Php 90,000
                    t = 5 years
                    n = 4(5) = 20 payments
                   i(4) = 0.06
                   m = 4 (compounded quarterly)
                         0.06
                    j=        = 0.015
                          4
      Find:        P=?
                                                                  19 | P a g e
                              1 − ( 1 + j )−n
        Formula:    P = R
                                     j
                                         1− ( 1 + 0.015 )−20
                    P = Php 90,000
                                                0.015
P = Php 1,545,177.49
       Therefore, the second offer has a greater fair market value at the given
focal date. The difference in the fair market values of the two offers at the
start of the term is:
       Php 1,645,177.49 - Php 1,584,940.84 = Php 60,236.65
What if the focal date is at the end of the term? Let’s find out.
      So, even though we have different focal dates, the second offer still has
a higher fair market value. The difference between the market values of the
two offers at the end of the term is:
      Php 2,215,815.54 - Php 2,134,685.50 = Php 81,130.04
Solution:
      Assume that the selected focal date is the start of the term. So, since
the focal date is at the start of the term, compute for the present value for
each investment offer.
Company A offer:
The present value of Php 400,000 three years from now is:
      P1 = F ( 1 + j )-n
      P1 = Php 400,000 ( 1 + 0.04)-6
      P1 = Php 316,125.81
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Company B offer:
     Compute the present value of a general annuity with quarterly
payments but with semi-annual compounding at 8%.
                      F1 = F2
                     i4 4t                  i2 2t
           P(1+         )    = P(1+           )
                     4                      2
                      i4 4               0.08 2
               (1+     ) = (1+               )
                     4                    2
                     i4 4
               (1+      )    = ( 1.04 )2
                     4
                       i4
                 1+        = [(1.04)2]1/4
                      4
                      i4
                             = ( 1.04 )1/2 – 1
                       4
                      i4
                            = 0.0198039 = j
                       4
P = Php 819,120.97
Deferred Annuity
      Deferred annuity refers to an annuity that does not begin until a given
interval has passed. For a deferred annuity, payments could be set on a later
or future date as agreed upon by the contract.
22 | P a g e
      Period of deferral refers to the time between the purchase of an annuity
and the start of the payments for the deferred annuity.
                                                                            23 | P a g e
       Example 2. In purchasing appliances, a credit card company offers
deferred payment options. A card holder plans to buy a smart television set
with monthly payments of Php 7,000 for 1 year. The payments will start at
the end of 3 months. How much is the cash price of the television set if the
rate is 8.1% compounded monthly?
       Given:    R = Php 7,000
                 m = 12
                 i12 = 0.081
                 k=2       (number of artificial payments)
                 n = 12 (number of actual payments)
                     0.081
                 j=         = 0.00675
                      12
       Find:     P=?
P = Php 79,352.83
Activities
24 | P a g e
      Find:       F=?
                           ( 1 + j )n − 1
      Formula:    F = R
                                 j
                                                                  25 | P a g e
C. Find the periodic payments R of a simple ordinary annuity that pays
monthly payment of the future value of Php 150,000 for 2 years with an
interest rate of 7.2% compounded monthly.
      Given:        F=
                    i12 =
                    m=
                          i12
                     j=       =
                           m
                     t=
                    n=
        Find:        R=?
                                    ( 1 + j )n − 1
        Formula:     F = R
                                          j
26 | P a g e
      2. Semi-annual payments of Php 30,000 with interest rate of 8%
compounded annually for 15 years
      Given:      R=
                   t=
                  n=
                  i1 =
                  m=
Steps:
      a. Convert 8% compounded annually to its equivalent interest rate for
semi-annual payment interval j.
      Use:
                           i2                           i1
              F1 = P ( 1 + 2 )2t              F2 = P ( 1 + 1 )1t
             (semi-annual payments)           (for compounded annually)
                      F1 = F2
                 i2 2t              i1 1t
        P(1+       )     = P(1+       )
                 2                  1
                      F1 = F2
                 i4                   i1 1t
        P(1+          )4t = P ( 1 +     )
                 4                    1
                                                                          27 | P a g e
      b. Apply the formula in finding the present value of an ordinary annuity
using the computed equivalent rate j.
                            1 − ( 1 + j )−n
      Formula:    P = R
                                    j
                    F1 = F2
                   i1 1t              i4 4t
           P(1+      )     = P(1+       )
                   1                  4
C. Fred received two offers for investment. The first offer is Php 180,000
every year for 5 years at 9% compounded annually. The other offer is
Php15,000 per month for 5 years with the same interest rate. Which fair
market value between these offers is preferable? (Compute the future value
using focal date as the end of the term.)
Solution:
First offer (Ordinary Annuity)
       Given:       R=
                    i1 =
                    m=
                    t=
                    n=
28 | P a g e
      Find:        F=
                               ( 1 + j )n − 1
      Formula:     F = R
                                       j
Steps:
      a. Convert 9% compounded annually to its equivalent interest rate for
monthly payment interval j.
                             i12 12t                                i1 1t
              F1 = P ( 1 +      )                    F2 = P ( 1 +     )
                             12                                     1
              (for monthly payments)            (for compounded quarterly)
Independent Practice
Solve each problem completely and logically.
A. Find the future value F of the following simple and general ordinary
annuities.
     1. Semi-annual payments of Php 8,000 with interest rate of 7%
           compounded semi-annually for 15 years
B. Find the present value P of the following simple and general ordinary
annuities.
     1. Monthly payments of Php 2,000 for 1 year with an interest rate of
         15% compounded monthly
                                                                            29 | P a g e
        2. Annual payments of Php 50,000 with an interest rate of 7%
           compounded annually for 20 years
        4. Mae availed a loan from a bank that gave her an option to pay
           Php30,000 monthly for 2 years. The first payment is due after 4
           months. How much is the present value of the loan if the interest
           rate is 10.5% compounded monthly?
        5. Bonn decided to sell their farm and to deposit the fund in a bank.
           After computing the interest, they learned that they may withdraw
           Php500,000 yearly for 10 years starting at the end of 8 years when
           it is time for him to retire. How much is the fund deposited if the
           interest rate is 6.5% converted annually?
30 | P a g e
5|P age
   Independent Practice            Review
   A.                              1, P = Php20,000 i12 = 0.04
   1. F = Php 412,981.42               j = 0.0033333 n = 60
   2. F = Php 922,758.25           2. P = Php50,000 i2 = 0.075
   3. F = Php 315,321.78               j = 0.0375     n = 20
   B.                                  F = Php104,407.60
   1. P = Php 22,158.62            3. F = Php80,000 i12 = 0.06
   2. P = Php 529,700.71               j = 0.005     n = 24
   3. P = Php 111,412.36               P = Php70,974.85
   C.
   1. R = Php 4,677.43             Guided Practice 1
   2. R = Php 18,397.83            A1. R=Php5000 i12 =0.03 m=12 j=0.0025
   3. first offer                      t=4 n= 48 F=Php254,656.04
            F = Php 1,270,569.47   2. R=Php2,500 i12 =0.05 m=4 j=0.0125
      second offer                     t=10 n= 40 F=Php128,723.89
            F = Php 1,285,460.34   B1. R=Php3000 i12 =0.12 m=12 j=0.01
    second offer is better             t=5 n= 60 P=Php134,865.12
   4. P = Php 630,197.88           2. R=Php20000 i2 =0.075 m=2 j=0.0375
   5. P = Php 2,315,028.46             t=6 n= 12 P=Php190,453.88
                                   C. F=Php150000 i12 =0.072 m=12
   Assessment                         j=0.006 t=2 n= 24 R=Php5,829.50
   1. c
   2. a                            Guided Practice 2
   3. b                            A1. R=Php5000 t=10 n=120
   4. d                                 i4=0.06 m=4 j=0.00497521
   5. d                                 F=Php818,075.23
   6. a                            2. R=Php30000 t=15 n=30
   7. c                                 i=0.08 m=1 j=0.03923048
   8. d                                 F=Php1,661,082.43
   9. b                            B1. R=Php20000 t=10 n=40
   10. a                                i=0.075 m=1 j=0.0182446
                                        P=Php564,338.00
                                   2. R=Php100000 t=20 n=20
                                        i4=0.05 m=4 j=0.05094534
                                        P=Php1,236,292.16
                                   C. a. first offer
                                      R=Php180,000 i=0.09 m=1
                                       t=5 n=5 F=1,077,247.91
                                      b. second offer
                                      R=Php15,000 i=0.09 m=1
                                       t=5 n=60 j=0.00720732
                                       F=1,120,992.93
                                    Second offer is better
                                   Key to Corrections