Find the HCF of 48 and 80.

Correct answer: 16. 48 = 2⁴ × 3 and 80 = 2⁴ × 5, so the HCF is 2⁴ = 16.

Background: The HCF is found by multiplying the common prime factors with their lowest powers.

• 8: 8 is a common factor but not the highest.
• 20: 20 does not divide 48.
• 22: 22 does not divide 48 or 80.

Did you know? For two numbers, HCF × LCM = product of the numbers. Here LCM = 240 and 16 × 240 = 48 × 80.

Memory trick: HCF = common primes, lowest power.