Question

Out of 15, 16, 21 and 28, find out all the pairs of co-prime numbers.

Answer 1

The pair will be 15 − 16, 16 − 21, 21 − 28, 15 − 28 and 16 − 28, 15 − 28 and 16 − 28...

The HCF of 15 and 16

and HCF of 21 and 28
HCF of 16 and 21  HCF of 13, 28

HCF of 16, 28

From above it is clear that 15 and 16 are co-prime because the common factor is 1
Hence pairs 15 and 16, 16, 21, 15, 28 are the co-prime numbers.