Find the common factors of the following.
i. 12 and 16
ii. 15 and 21

Given :

The given numbers are:

i. 12 and 16
ii. 15 and 21

To do :

We have to find the common factors of the given numbers.

Solution :

(i) Factors of 12 are 

$12 = 1\times 12 = 2\times 6 = 3\times 4$

Therefore, factors of 12 are 1, 2, 3, 4, 6 and 12.

Factors of 16 are

$16 = 1\times 16 = 2\times 8 = 4\times 4$

Therefore, factors of 16 are 1, 2, 4, 8 and 16.

The common factors of 12 and 16 are 1, 2 and 4.

 (ii) Factors of 15 are 

$15 = 1\times 15 = 3\times 5$

Therefore, factors of 15 are 1, 3, 5 and 15.

Factors of 21 are

$21 = 1\times 21 = 3\times 7$

Therefore, factors of 21 are 1, 3, 7 and 21.

The common factors of 15 and 21 are 1 and 3.