How do you find the LCM of 15 and 20?

Answer 1

3 x 5 = 15

2 x 2 x 5 = 20

2 x 2 x 3 x 5 = 60, the LCM

Answer 2

In this case, you can just try out multiples of 20 (20 x 1, 20 x 2, etc.), and see which of them is also a multiple of 15.