18, 36, 54, 72, 90, 108.
First three common multiples of 2 and 6 are 6, 12 and 18.
The first three common multiples are 18, 36, and 54.
The first five multiples of 6 are 6, 12, 18, 24 and 30. For them to be common, they need to be compared to another set of multiples.
They are: 6, 12 and 18
3: 3, 6, 9, ... 6: 6, 12, 18, ... 18: 18, 36, 54, ... The lcm(3, 6, 18) = 18, so the multiples of 18 are common multiples of all of them.
The common multiples of 6 and 9 are the infinite set of multiples of their LCM, which is 18. So the common multiples of 6 and 9 are 18, 36, 54, 72, 90, 108, 126, 144, 162, 180, and so on.
6, 12 and 18
6, 12, 18
6, 12, 18, 24
6, 12, 18
18, 36, 54
Multiples of 6 include 6, 12 and 18. For them to be common, they need to be compared to another set of multiples.