Question

Using set theory, find the HCF of 12,15and18

Answer 1

Let the prime factors of the numbers be named set A, B and C. Where,

A = {2, 2, 3} ( Factors of 12)
B = {3, 5}. ( Factors of 15)
C = {2, 3, 3} (Factors of 18)

HCF( 12, 15, 18) = A interception B interception C
= { 3 }

Hence HCF = 3