We have :
6=2×3,
72=23×32,
120=23×3×5
Here, 21 and 31 are the smallest powers of the common factors 2 and 3 respectively.
So, HCF (6, 72, 120) =21×31=2×3=6
Also, 23, 32 and 51 are the greatest powers of the prime factors 2, 3 and 5 respectively involved in the three numbers.
So, LCM (6, 72, 120) =23×32×51=360