Question 3

Find the LCM and HCF of the following integers by applying the prime factorisation method.

(i) 12, 15 and 21

Step 1: Prime factorisation

12 = 2² × 3
15 = 3 × 5
21 = 3 × 7

Step 2: HCF

Common prime factor = 3
HCF = 3

Step 3: LCM

LCM = 2² × 3 × 5 × 7
LCM = 420