1. 1. Factors
• What is the factors?

2. What does the symbol “÷” and “ = ” mean?
12÷3 = 4
18÷9 = 2
15÷4 = 3R3
Review

3. The symbol “ ” is “ division”
The symbol “ = ” is “ division”
Therefore
12÷3 = 4
We can read that “ twelve divide
three equals four

4. • 18÷9 = 2
• We can read that “ eight
divide nine equals two

5. • What about?
15÷4 = ?

6. 12÷3 = 4
If 12 can be divided by 3, so 3 is a factor of 12
18÷9 = 2
If 18 can be divided by 9, so 9 is a factor of 18
15÷4 = 3.75
If 15 cannot be divided by 4, so 4 is not a factor of 15

7. (A) Determine whether the given number is a
factor of the number in brackets.
• (a). 2 (14)
• (b). 5 (120)
• (c). 8 (124)
• (d). 12 (106)
• (e). 15 (145)
• (f). 21 (105)

8. (B) List the factors of a whole
number

10. 24
2 12
2 6
2 3
List down all the factors of 24
1
24 can be divided by 2, 3, 6, 12 and 24.
So, the factors of 24 are 2, 3, 6, 12 and 24.

11. 2. Prime factors
• (A) Prime numbers
A prime number is a
whole number that
has only two factors,
that is 1 and itself.

12. Example
•Determine whether the
following are prime
numbers: 4, 6, 7, 9, and
13

13. • 4 has three factors: 1, 2,and 4
4 prime number.

14. • 7 has two factors: 1 and 7
7 is a prime number

15. • 9 has three factors: 1, 3 and 9
9 is not a prime number

16. • 13 has two factors: 1 and 13
13 is a prime number

17. • prime numbers from 1-100have 25 numbers:
2, 3, 5, 7, 11, 13, 17, 19, 23, 29,
31, 37, 41, 43, 47, 53, 59, 61, 67,
71, 73, 79, 83, 89 and 97

18. Greatest Common Divisor (GCD)
Example Find the common divisor and the greatest common factor
(GCD) of 8 and 20
factor of 8 = 1, 2, 4 and 8.
factor of 20 are 1, 2, 4, 5, 10 and 20
1, 2, 4 are the common divisors of 8 and 20
4 is the greatest common divisor of 8 and 20

19. Exercise 1
• Find the GCD of following pairs of number.
• 1) 2, 15……………..
• 2) 5, 10……………..
• 3) 12, 2……………..
• 4) 8, 40……………..
• 5) 6, 8………………..

20. Least common multiple(LCM)
• 1.) 4 and 8 LCM=
• 2.) 12 and 18 LCM=