Question

What is the highest common factor of 28 and 42?

• A. 1
• B. 7
• C. 4
• D. 14

Answer 1

The correct option is D 14

28 = 1 $\times$ 28
28 = 2 $\times$ 14
28 = 4 $\times$ 7
So, the factors of 28 are 1, 2, 4, 7, 14 and 28.

42 = 1 $\times$ 42
42 = 2 $\times$ 21
42 = 3 $\times$ 14
42 = 6 $\times$ 7
So, the factors of 42 are 1, 2, 3, 6, 7, 14, 21 and 42.

Therefore, the highest common factor of 28 and 42 is 14.