# Which pair of numbers does not have the HCF as 1?

# a) 2 and 5 b) 3 and 5 c) 2 and 6 d) 6 and 7

## Answer: option (c) - The HCF of 2 and 6 is not 1.

**Explanation:**

Let us find the HCF of each of the above options.

HCF of 2 and 5

HCF of 2 and 5 is 1

b) HCF of 3 and 5

The highest common factor of 3 and 5 is 1

HCF of 3 and 5 is 1

c) HCF of 2 and 6

Common Factors of 2 and 6 : 1 and 2

The highest common factor is 2

HCF of 2 and 6 is 2

d) HCF of 6 and 7

The only common factor of 6 and 7 is 1

Therefore, HCF of 6 and 7 is 1