Find the HCF and LCM of 12, 15, 18, 27.
12 = 2 × 2 × 3
15 = 3 × 5
18 = 2 × 3 × 3
27 = 3 × 3 × 3
So HCF = 3
And LCM = product of prime factors with highest powers = 22 × 33 × 5 = 540