Question

Which of the following is a pair of co-primes?

Options

• (14, 35)

• (18, 25)

• (31, 93)

• (32, 62)

Answer 1

(18, 25)

Explanation:

18 = 2 × 3² and 25 = 5² they share no prime factors, so gcd(18, 25) = 1 they are co-prime.

For comparison: (14, 35) have gcd 7; (31, 93) have gcd 31; (32, 62) have gcd 2.