15 & 20 have an infinite number of Common Multiples; the first three are 60, 120 and 180.
10, 20, 30 The common multiples of 5 and 10 are multiples of their lowest common multiple. The lcm of 5 and 10, is 10. Thus the first three common multiples are 10, 20, 30.
20 is the smallest common multiple of 4, 5, and 10, and thus the first. Thus, the first three common multiples of 4, 5, and 10 are 20, 40 and 60.
40, 80 & 120.
10, 20, 30.
They are: 180, 360 and 540
100, 200, 300
20, 40 and 60
20, 40, 60.
10, 20, 30.
20 30 40
140, 280, 420