The LCM of 42 and 70 is 210. To find the LCM (least common multiple) of 42 and 70, we need to find the multiples of 42 and 70 (multiples of 42 = 42, 84, 126, 168 . . . . 210; multiples of 70 = 70, 140, 210, 280) and choose the smallest multiple that is exactly divisible by 42 and 70, i.e., 210.