Which pair of composite numbers has a GCF of 1?

Answer 1

Two composite numbers are considered relatively prime if their greatest common factor (GCF) is 1. For example, the pair of composite numbers 15 and 28 have a GCF of 1 because the factors of 15 are 1, 3, 5, and 15, while the factors of 28 are 1, 2, 4, 7, 14, and 28, and they do not share any common factors other than 1. Another example is the pair of composite numbers 21 and 34, as their factors are 1, 3, 7, 21 and 1, 2, 17, 34 respectively, and their GCF is also 1.

Answer 2

There are infinitely many such pairs.

For example,

suppose p, q, r and s are 4 prime numbers.

Then p*q and r*s are both composite but p*q and r*s are coprime.

And you could always mutiply either one of them by the prime number t, and maybe the other one by another r to give p*q*t and r2*s. And so on.

The smallest pair of composites is 14 and 15.

Answer 3

4 and 9