Question

Using prime factorization, find the HCF and LCM of  21, 28, 36, 45 .

Answer 1

21 = 3 × 7
28 = 2 × 2 × 7 = 2² × 7
36 = 2 × 2 × 3 × 3 = 2² × 3²
45 = 5 × 3 × 3 = 5 × 3²
HCF = product of smallest power of each common prime factor in the numbers = 1
LCM = product of greatest power of each prime factor involved in the numbers
= 2² × 3² × 5 × 7 = 1260