Question

Using the prime factorisation method, the HCF of 72 and 90 is:

Options

• 12

• 18

• 36

• 6

Answer 1

18

Explanation:

72 = 2 × 2 × 2 × 3 × 3 and 90 = 2 × 3 × 3 × 5.

Common primes: 2 × 3 × 3 = 18.