What is the LCM of 21 and 35 and 42?

Answer 1

Note that 21 x 2 = 42, so we really only need to look at 35 and 42.

So 7 x 5 = 35, and 7 x 6 = 42. There is a common factor of 7. So we have 7 x 5 x 6 = 210 is the LCM.

Answer 2

The LCM is 210.