## EXERCISE 3.4 1 Find the common factors of (a) 20 and 28 (b) 15 and 25 (c) 35 and 50 (d) 56 and 120 2. Find the common factors

EXERCISE 3.4

1 Find the common factors of

(a) 20 and 28 (b) 15 and 25 (c) 35 and 50 (d) 56 and 120

2. Find the common factors of –

(a) 4,8 and 12 (b) 5.15 and 25

3. Find first three common multiples of

(a) 6 and 8

(bol 2 and 18

4. Write all the numbers less than 100 which are common multiples of 3 and 4.

5. Which of the following numbers are co-prime?

(a) 18 and 3 (b) is and 37

(c) 30 and 415

(d) 17 and 68 (e) 216 and 215 ( 81 and 16

6. A number is divisible by both 5 and 12. By which other number will that number be

always divisible?

7. A number is divisible by 12. By what other numbers will that number be divisible?

## Answers ( )

Answer:1(a) 20=(2)(2)(4)

28= (2) (2) (7)

common factors = (2) (2)

= 4

(note : ( ) indicates the sign of multiplication