The numbers that can divide an integer is called its factor or divisor.

For example, the factors of 4 are 1, 2, and 4 because

these are the numbers that divide 4 without having a remainder. Another example is 6 which has factors 1, 2, 3, and 6. It
is clear that each number has always 1 and itself as factors. Note that in this discussion, when I say number, I mean
positive integer.

If we select more than one number, we can observe that they have common factors (just like having common multiples).
Let’s have the following examples.

How to Get the Greatest Common Factor of Numbers

Example 1: What are the common factors of 12 and 18?

Factors of 12: 1, 2, 3, 4, 6, 12

Factors of 18: 1, 2, 3, 6, 9, 18

If we examine the factors of 12 and 18, we see that there are 4 common factors: 1, 2, 3 and 6. Among the factors, 6 is
the largest. Therefore, we say that 6 is the greatest common factor (GCF) or greatest common divisor (GCD) of 12 and
18.
Example 2 : Find the GCF of 20, 32, 28.

Factors of 20: 1, 2, 3, 4, 5, 10, 20

Factors of 32: 1, 2, 4, 8, 16, 32

Factors of 28: 1, 2, 4, 7, 14, 28

As we can see, the common factors of 20, 32, and 28 are 1, 2, and 4. The GCD or GCF of the three numbers is 4.

Another way to get the greatest common factor of numbers is to write their prime factorization. Prime factorization is
the process of expressing a number as product of prime numbers. A prime number is a number which is only divisible by
1 and itself (read Introduction to Prime Numbers if you don’t know what a prime number is). The first 10 prime numbers
are 2, 3, 5, 7, 11, 13, 17, 19, 23, and 29.

We will use the examples above and use prime factorization in order to get their greatest common factor.

Example 3: Find the GCF of 12 and 18 using prime factorization.

Prime factorization of 12: 2 × 2 × 3

Prime Factorization of 18: 2 × 3 × 3

Now to get the greatest common factor, we multiply the common factors to both numbers. The common factors to both
are 2 and 3, therefore, the greatest common factor of 12 and 18 is 2 × 3 = 6.

Example 4: Find the GCF of 20, 32, and 28 using prime factorization.

Prime factorization of 20: 2 × 2 × 5

Prime factorization of 32: 2 × 2 × 2 × 2 × 2

Prime factorization of 28: 2 × 2 × 7

In this example, 2 and 2 are common to all the three numbers, so the GCD or GCD of these three numbers is 2 × 2 which
is equal to 4.

The difference between the two methods is that in the first method, you list all the factors and find the largest number.
In the second method, you list the prime factorization and the multiply the factors that are common to all numbers.

●CONVERSION OF DECIMAL TO FRACTION●

1.1 (remove the decimal point) = 11/10
1.11 (remove the decimal point) = 111/100
1.111 (remove the decimal point) = 1111/1000
Technique: titignan po natin kung ilan yung digit after ng decimal point.
1 digit = over 10
2 digits = over 100
3 digits = over 1,000
●CONVERSION OF PERCENT TO FRACTION●
1% = 1/100 (percent means hundreds kaya over 100)
1.1% (remove the decimal point & %) = 11/1000 (over 100 yung 1% e may 1 digit after decimal point 1 digit means
additional 1 ZERO(0) kaya over 1,000 xa)
1.11% (remove the decimal point & %) = 111/10,000 (over 100 yung 1% e may 2 digits after decimal point, 2 digits
means additional 2 ZEROS(0) po kaya over 10,000 po xa)
●CONVERSION OF DECIMAL TO PERCENT●
1.1 (move the decimal point two places to the right) = 110%
1.11 (move the decimal point two places to the right) = 111%
1.111 (move the decimal point two places to the right) = 111.1%
●CONVERSION OF FRACTION TO PERCENT●
1/100 (1 divided by 100 > 0.01 > move the decimal point two places to the right) = 1%
11/1000 (11 divided by 1000 > 0.011 > move the decimal point two places to the right) = 1.1%
111/10000 (111 divided 10000 > 0.0111 > move the decimal point two places to the right) = 1.11%
●CONVERSION OF PERCENT TO DECIMAL●
1.1% (move the decimal point two places to the left) = 0.011
1.11% (move the decimal point two places to the left) = 0.0111
1.111% (move the decimal point two places to the left) = 0.01111
●CONVERSION OF FRACTION TO DECIMAL●
11/10 (11 divided by 10) = 1.1
111/100 (111 divided by 100) = 1.11
1111/1000 (1111 divided by 1000) = 1.111

WHOLE NUMBER - siya po yung number na walang fraction bar/line.

NUMERATOR - siya po yung number na nasa itaas ng fraction bar/line.
DENOMINATOR - siya po yung number na nasa ibaba ng fraction bar/line.
PROPER FRACTION - mas mababa po yung number sa numerator kaysa sa denominator. Ex. 1/2
IMPROPER FRACTION - mas mataas yung number sa numerator kaysa sa denominator. Ex. 3/2
MIXED FRACTION/NUMBER - may whole number, numerator at denominator. Ex. 1 2/3
NOTE: lahat po ng sagot sa pag-add, subtract, multiply, divide ng fraction ay dapat naka-reduce sa lowest terms.

1. 1/3 + 3/5
SOLUTION:
Kailangan po natin kunin yung Least Common Denominator (LCD) sa mga fraction na magkaiba yung denominator bago
po natin sila ma-i-add o ma-i-subtract. Sa tanong po, 15 po yung LCD. I-di-divide po natin sila sa denominator, multiply sa
numerator at over po sila sa denominator.
1/3 + 3/5 =
(15÷3*1 over 15) + (15÷5*3 over 15) =
5*1 over 15 = 5/15
+
3*3 over 15 = 9/15
5/15 + 9/15 = 14/15 √

2. 1 1/3 + 1 3/5
SOLUTION:
Sa addition & subtraction po ng mixed fraction/number, kailangan po muna natin i-convert sa improper fraction bago
natin sila ma-i-add o subtract. Kailangan natin i-multiply yung whole number sa denominator, i-add yung numerator at i-
over sa denominator at pagkatapos po kukunin natin yung LCD ng dalawang denominator para ma-i-add o sutract natin
sila. Kailangan po na magkamukha yung denominator bago natin sila ma-i-add o subtract.
1 1/3 + 1 3/5
(1*3+1 over 3) +
(1*5+3 over 5) =
3+1 over 3 = 4/3
+
5+3 over 5 = 8/5
4/3 + 8/5
LCD: 15
(15÷3*4 over 15) +
(15÷5*8 over 15)
5*4 over 15 = 20/15
3*8 over 15 = 24/15
44/15
Kailangan po natin i-convert yung improper fraction na 44/15 sa mixed fraction/number.
44÷15 = 2 14/15 √

3. 1/3 - 3/5
SOLUTION:
Paki-tignan po yung paliwanag sa question #1.
1/3 - 3/5
LCD: 15
(15÷3*1 over 15) -
(15÷5*3 over 15)
5*1 over 15 = 5/15
-
3*3 over 15 = 9/15
5/15 - 9/15 = -4/15 √

4. 1 1/3 - 1 3/5
SOLUTION:
Paki-tignan po yung paliwanag sa question #2.
(1*3+1 over 3) -
(1*5+3 over 5)
3+1 over 3 = 4/3
-
5+3 over 5 = 8/5
4/3 - 8/5
LCD: 15
(15÷3*4 over 15) -
(15÷5*8 over 15)
5*4 over 15 = 20/15
3*8 over 15 = 24/15
20/15 - 24/15 = -4/15 √

5. 1/3 X 3/5
SOLUTION:
Sa multiplication of proper fraction, i-mu-multiply po natin yung mga numerator sa isa't isa at yung mga denominator sa
isa't isa.
1/3 X 3/5
1*3 over 3*5
3/15
Pareho po silang divisible ng 3.
3÷3, 15÷3 = 1/5 √

6. 1 1/3 X 1 3/5
SOLUTION:
Sa multiplication of mixed fraction/number, kailangan po muna natin i-convert sa improper fraction at i-multiply po
natin yung mga numerator at denominator sa isa't isa.
1 1/3 X 1 3/5
(1*3+1 over 3) X
(1*5+3 over 5)
3+1 over 3 = 4/3
5+3 over 5 = 8/5
4/3 X 8/5
32/15
Kailangan po natin i-convert yung improper fraction sa mixed fraction/number.
32/15 = 2 2/15 √

7. 1/3 ÷ 3/5
SOLUTION:
Sa division of proper fraction, kailangan po kunin yung reciprocal o baligtaran yung mga number sa fraction after ng (÷)
sign.
1/3 ÷ 3/5
1/3 X 5/3
I-mu-multiply po natin yung mga numerator at denominator sa isa't isa.
1*5 over 3*3
5/9 √

8. 1 1/3 ÷ 1 3/5
SOLUTION:
Sa division of mixed fraction/number, kailangan po muna natin i-convert sa improper fraction.
1 1/3 ÷ 1 3/5
(1*3+1 over 3) ÷
(1*5+3 over 5)
3+1 over 3 = 4/3
÷
5+3 over 5 = 8/5
4/3 ÷ 8/5
Kailangan po natin kunin yung reciprocal ng mga number sa fraction after ng (÷) sign.
4/3 ÷ 8/5
4/3 X 5/8
Kailangan po natin i-multiply yung mga numerator at denominator sa isa't isa.
4/3 X 5/8
4*5 over 3/8
20/24
Divisible po sila ng 4
20÷4, 24÷4 = 5/6 √

9. Simplify: 35/555
SOLUTION:
Mag-i-isip po tayo ng isang number na pwedeng i-divide sa numerator at denominator na ang sagot ay kailangang whole
number.
35/555
Divisible po sila sa 5.
35÷5, 555÷5 = 7/111 √

10. Simplify: 36/600

SOLUTION:
Paki-tignan po yung paliwanag sa question #9.
36/600
Divisible po sila sa 6.
36÷6, 600÷6 =
6/100
Divisible po sila sa 2.
6÷2, 100÷2 = 3/50 √

11. Simplify: 54/658

SOLUTION:
Paki-tignan po yung paliwanag sa question #9.
54/658
Divisible po sila sa 2.
54÷2, 658÷2 = 27/329 √

12. 2/6, 5/12, 9/19, ____

SOLUTION:
Titignan po natin lahat ng numerator at denominator.
Numerators - 2, 5, 9, ___
Denominators - 6, 12, 19, ___
2 (+3), 5 (+4), 9 (+5) = 14
6 (+6), 12 (+7), 19 (+8) = 27
14/27 √
(NOTE: Hindi po natin i-re-reduce sa lowest terms yung fraction sa number series involving fraction.)

13. 8/48, 27/59, 64/70, ____

SOLUTION:
Titignan po natin lahat ng numerator at denominator.
Numerators - 8, 27, 64, ___
Denominators - 48, 59, 70, ___
2*2*2 = 8
3*3*3 = 27
4*4*4 = 64
5*5*5 = 125
48 (+11), 59 (+11), 70 (+11) = 81
125/81 √

14. 8/11, 64/111, 216/1111, ____

SOLUTION:
Titignan po natin lahat ng numerator at denominator.
Numerators - 8, 64, 216, ___
Denominators - 11, 111, 1111, ____
2*2*2 = 8
4*4*4 = 64
6*6*6 = 216
8*8*8 = 512
NOTE: Even number po lahat (2, 4, 6, 8), 2^3, 4^3, 6^3, 8^3.
11 (two number 1), 111 (three number 1), 1111 (four number 1), 11111 (five number 1)
512/11111 √

15. 27/10000, 125/10000, 729/10000, ____

SOLUTION:
Titignan po natin yung lahat ng numerator at denominator.
Numerators - 27, 125, 729, ____
Denominators - 10000, 10000, 10000, ____
3*3*3 = 27
5*5*5 = 125
9*9*9 = 729
15*15*15 = 3,375
NOTE: Odd number po lahat. 3 (+2) 5 (+4) 9 (+6) 15. 3^3, 5^3, 9^3, 15^3
Iisa lang po yung mga denominator = 10,000
3,375/10,000 √

DECIMALS
1) 1.2345 + 123.45 + 1234.5 + 12.345
SOLUTION:
Sa addition & subtraction of numbers in decimals, sa addition of numbers in decimals na may kasamang whole numbers,
kailangan po muna natin pag-tapat-tapatin lahat ng may decimal point bago tayo makapag-add o subtract. Simula po sa
kanan papunta sa kaliwa yung pag-a-add o pag-su-subtract. Uunahin po natin yung mas mataas sa value sa pag-su-
subtract. Pwede po maging negative yung sagot. Nilagyan ko po siya ng zeros para mas maipakita ko po kung papaano
sila ma-i-so-solve.
000001.2345
000123.4500
+01234.5000
000012.3450
001371.5295 √

2) 123.45 + 12.34 + 123 + 1234.5 + 1.23

SOLUTION:
Paki-tignan po yung paliwanag sa question #1.
000123.45
000012.34
000123.00
+01234.50
000001.23
001494.52 √

3) 1234.5 - 123.4
SOLUTION:
Paki-tignan po yung paliwanag sa question #1.
01234.50
--0123.40
01111.1 √
4) 123.45 - 1.2345
SOLUTION:
Paki-tignan po yung paliwanag sa question #1.
00123.4500
--0001.2345
00122.2155 √

5) 1.23 X 12.3 (3 decimal places)

SOLUTION:
Sa multiplication of numbers in decimals, sa multiplication of numbers in decimals na may kasamang whole numbers,
kailangan po natin pag-tapat-tapatin yung mga decimal point nila bago natin sila i-multiply. Para malaman natin kung
tama yung sagot, kailangan natin bilangan kung ilang decimal places meron ang bawat isa at yun po ay ang dami ng
numbers after decimal point. Pagsasamahin po natin sila. Ex. 1.2 X 2.3 (1.2 -- 1 decimal place) (2.5 -- 1 decimal place) = 2
decimal places. Ang sagot po ay 2.76 na may 2 decimal places. (Nilagyan po sila ng zeros para maipakita ko po kung
paano sila ma-i-so-solve.)
000001.230
X00012.300
000015.129 √(3 decimal places)

6) 123.4 X 1.2 (2 decimal places)

SOLUTION:
Paki-tignan po yung paliwanag sa question #5.
123.40
X01.20
148.08 √ (2 decimal places)

7) 123 X 1.23 (2 decimal places)

SOLUTION:
Paki-tignan po yung paliwanag sa question #5.
00123.00
X0001.23
00151.29 √ (2 decimal places)

8) 12.34 ÷ 1.23
SOLUTION:
Sa division of numbers in decimals, sa division of numbers in decimals na may kasamang whole numbers, kailangan po
muna natin silang gawing whole number lahat bago natin sila ma-i-divide. Kailangan po natin i-move yung decimal point
papunta sa gawing kanan para maging whole number sila. Kung ilang beses po natin na-i-move yung decimal point ng
isa, gawin din po dapat yung isa.
Ex. 2.3 (move the decimal point one place to the right) = 23
÷ 1.2 (move the decimal point one place to the right) = 12
23 ÷ 12 = 1.92 (rounded off po siya up to two decimal places, depende po sa tanong kung ilang decimal places po dapat
i-round off)
12.34 ÷ 1.23
1234 ÷ 123
10.03 √ (rounded off po siya up to two decimal places)

9) 1.234 ÷ 12.3
SOLUTION:
Paki-tignan po yung paliwanag sa question #8.
1.234 ÷ 12.3
1234 ÷ 12300
0.1 √ (rounded off po siya up to one decimal place)

10) 123 ÷ 1.23

SOLUTION:
Paki-tignan po yung paliwanag sa question # 8.
123 ÷ 1.23
12300 ÷ 123
100 √

11) 1.23, 2.46, 7.38, 29.52, ___

SOLUTION:
1.23, (X 2) 2.46, (X 3) 7.38, (X 4) 29.52, (X 5) 147.6 √

12) 2.37, 7.11, 35.55, 248.85, ___

SOLUTION:
2.37, (X 3) 7.11, (X 5) 35.55, (X 7) 248.85, (X 9) 2239.65 √

13) 3.58, 12.11, 20.64, 29.17, ___

SOLUTION:
3.58, (+8.53) 12.11, (+8.53) 20.64, (+8.53) 29.17, (+8.53) 37.7 √

14) 17.56, 16.33, 15.1, 13.87, ___

SOLUTION:
17.56, (-1.23) 16.33, (-1.23) 15.1, (-1.23) 13.87, (-1.23) 12.64 √

15) 2.88, 5.76, 11.52, 23.04, ___

SOLUTION:
2.4, (X 2) 5.76, (X 2) 11.52, (X 2) 23.04, (X 2) 46.08 √

NUMBERS
WHOLE NUMBERS - 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and so on.

1) 2, 5, 11, 20, ___

SOLUTION:
2, (+3) 5, (+6) 11, (+9) 20, (+12) 32 √

2) 60, 30, 20, 15, 12, ___

SOLUTION:
60÷1=60
60÷2=30
60÷3=20
60÷4=15
60÷5=12
60÷6=10 √

3) 4, 8, 32, 192, ___

SOLUTION:
4, (X 2) 8, (X 4) 32, (X 6) 192, (X 8) 1536 √

4) 5, 15, 75, 525, ___

SOLUTION:
5, (X 3) 15, (X 5) 75, (X 7) 525, (X 9) 4725 √
5) 4, 16, 36, 64, ___
SOLUTION:
2X2=4
4X4=8
6 X 6 = 36
8 X 8 = 64
10 X 10 = 100 √

6) 1, 9, 25, 49, ___

SOLUTION:
1X1=1
3X3=9
5 X 5 = 25
7 X 7 = 49
9 X 9 = 81 √

7) 1, 16, 81, 256, ___

SOLUTION:
1X1X1X1=1
2 X 2 X 2 X 2 = 16
3 X 3 X 3 X 3 = 81
4 X 4 X 4 X 4 = 256
5 X 5 X 5 X 5 = 625 √

8) 31, 59, 21, 87, 115, 21, ___, ___

SOLUTION:
Number 21 was repeated.
31, (+28) 59, (+28) 87, (+28) 115, (+28) 143, (+28) 171
143, 171 √

COUNTING NUMBERS - 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and so on.

EVEN NUMBERS - 0, 2, 4, 6, 8, 10, and so on.

ODD NUMBERS - 1, 3, 5, 7, 9, and so on.

PRIME & COMPOSITE NUMBERS

NOTE: The number 1 is neither prime nor composite because it only has one positive factor, which is itself.
PRIME NUMBER - a number which has exactly two factors; itself and one.
Ex. 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, and
so on.

COMPOSITE NUMBER - a number which can be represented by the product of two positive integers, neither of which
can be itself.
Ex. 4, 6, 8, 9, 10, 12, 14, 15, 16, 18, 20, and all the numbers that have not be mentioned to be composite numbers up
until 113, but there are a lot of composite numbers after 113.

POSITIVE & NEGATIVE INTEGERS

9) 6-18 = -12 √
10) -6-18 = -24 √
11) -6+18 = 12 √
12) 6-(-18) = 6+18 = 24 √
13) -6-(-18) = -6+18 = 12 √
14) 6 X 18 = 108 √
15) 6 X -18 = -108 √
16) -6 X 18 = -108 √
17) -6 X -18 = 108 √
18) 18 ÷ 6 = 3 √
19) 18 ÷ -6 = -3 √
20) -18 ÷ 6 = -3 √
21) -18 ÷ -6 = 3 √

*ADDITION OF INTEGERS*
*An integer with no sign means a positive(+) integer*
Positive(+) plus Positive(+) equals Positive(+)
Ex. 1+2=3
Positive(+) plus Negative(-) equals Positive(+) or Negative(-) depending on the sign of the higher number of the given
integers
Ex. 1-2 = -1 (2 is the higher number with a negative sign, so the sign must be negative)
Ex. 3-2 = 1 (3 is the higher number with a positive sign, so the sign must be positive)
Negative(-) plus Negative(-) equals Negative(-)
Ex. (-1)+(-2)= -3 *NOTE(-1)+(-2) is the same as -1-2 = +(-) = -
Negative(-) plus positive(+) equals Positive(+) or Negative(-) depending on the sign of the higher number of the given
integers
Ex. -2+1=-1 (2 is the higher number with a negative sign, so the sign must be negative)
Ex. -2+3= 1 (3 is the higher number with a positive sign, so the sign must be positive)

*SUBTRACTION OF INTEGERS*
Positive(+) minus Positive(+) equals Positive(+) or Negative(-) depending on the sign of the higher number of the given
integers
Ex. 2-1= 1 (2 is the higher number with a positive sign, so the sign must be positive)
Ex. 2-3= -1 (3 is the higher number with a negative sign, so the sign must be negative)
Positive(+) minus Negative(-) equals Positive(+)
Ex. 2-(-1) = 2+1= 3 *NOTE: -(-) = +
Negative(-) minus Negative equals Positive(+) or Negative(-) depending on the sign of the higher number of the given
integers
Ex. (-2)-(-1) = -2+1= -1 (2 is the higher number with a negative sign, so the sign must be negative). -(-)= +
Ex. (-5)-(-6) = -5+6 = 1 (6 is the higher number with a positive sign, so the sign must be positive)
Negative(-) minus Positive(+) equals Negative (-) *we have to copy the negative sign
Ex. -2-1 = -3
Ex. -2-3 = -5

*MULTIPLICATION OF INTEGERS*
Like/Same signs = Positive(+)
Unlike signs/Different/Not the same signs= Negative(-)
Ex. 1 * 2 = 2 (1 & 2 possess both positive signs) (* means times) {1*2 is the same as (1)(2) & 1 X 2}(Positive times Positive
equals Positive, that is like signs which need a positive sign)
Ex. 1 * -2 (1 with a positive sign & 2 with a negative sign) (Positive times Negative equals Negative, that is unlike signs
which need a negative sign)
Ex. -1 * -2 (1 with a negative sign & 2 with a negative sign) (Negative times Negative equals Positive, that is like signs
which need a Positive sign)
Ex. -1 * 2 (1 with a negative sign & 2 with a positive sign) (Negative times Positive equals Negative, that is unlike signs
which need a Negative sign)

*DIVISION OF INTEGERS*
*SAME RULES IN MULTIPLICATION OF INTEGERS MUST BE APPLIED IN DIVISION OF INTEGERS*
Ex. 2 ÷ 1 = 1(Like signs= Positive sign)
Ex. 2 ÷ -1 = -1(Unlike signs= Negative sign)
Ex. -2 ÷ -1 = 1(Like signs= Positive sign)
Ex. -2 ÷ 1 = -1(Unlike signs= Negative sign)

PLACE VALUE (whole numbers)

123,456,789
1 - hundred millions
2 - ten millions
3 - millions
4 - hundred thousands
5 - ten thousands
6 - thousands
7 - hundreds
8 - tens
9 - ones

PLACE VALUE (in decimal form)

12,345.6789
1 - ten thousands
2 - thousands
3 - hundreds
4 - tens
5 - ones
. - decimal point
6 - tenths
7 - hundredths
8 - thousandths
9 - ten thousandths

ROUNDING OFF NUMBERS

Kung ang number po sa right side ay:
1) 0-4 (i-re-retain lang po natin yung number sa left side tapos mag-a-add po tayo ng zero o zeros)
2) 5-9 (mag-a-add po tayo ng 1 sa number sa left side tapos mag-a-add po tayo ng zero o zeros)

Round off 123,456,789 to the nearest:

22) tens (8 is the tens digit) = 123,456,790 √
23) hundreds (7 is the hundreds digit) = 123,456,800 √
24) thousands = (6 is the thousands digit) = 123,457,000 √
25) ten thousands = (5 is the ten thousands digit) = 123,460,000 √
26) hundred thousands = (4 is the hundred thousands digit) = 123,500,000 √
27) millions = (3 is the millions digit) = 123,000,000 √
28) ten millions = (2 is the ten millions digit) = 120,000,000 √

Round off 2,345.6789 to the nearest:

29) thousands (2 is the thousands digit) = 2,000 √
30) hundreds (3 is the hundreds digit) = 2,300 √
31) tens (4 is the tens digit) = 2,350 √
32) whole number (ones/units) = (5 is the ones digit) = 2,346 √
33) tenths (6 is the tenths digit) = 2,345.7 √
34) hundredths (7 is the hundredths digit) = 2,345.68 √
35) thousandths (8 is the thousandths digit) = 2,345.679 √
Number divisible by 11:
Take the alternating sum of the digits if the answer is divisible by 11.
Example: 8470803=8-4+7-0+8-0+3= 22

Number divisible by 9:
The sum of all the digits is divisible by 9
Example: 3627 = 3+ 6+ 2 + 7 = 18

Number divisible by 8:
The last three digits are divisible by 8
Example: 456,791,824 and 923,780

Number divisible by 7:
Double the last digit and subtract it from the rest of the numbers it must be divisible by 7.
Example: 196 and 2023

Number divisible by 6:
The sum of all the digits are divisible by 2 and 3.
Examples:23,908 and 154, 608

Number divisible by 4:
If the last two digits are divisible by 4
Examples: 456,791,824 and

Number divisible by 3:
If the sum of all the individual digits is evenly divisible by 3.
Example: 3627
3+6+2+7 = 18