Any multiple of 30.
30, 60, 90
First three common multiples of 5 and 6 are 30, 60 and 90.
They are multiples of 60.
Any multiples of 20.
6,12,18,24,30,36,42,48,54,60,66,72,78,84,90,96,102 and blah, blah, and blah and so on..... There's 15 multiples of six for ya.
They are the six multiples of 15.
The common multiples of 5 and 6 are the multiples of their lowest common multiple (which is 30), so there are infinitely many common multiples of 5 and 6. The first five are: 30, 60, 90, 120, 150.
The first five multiples of 4 are 4, 8, 12, 16 and 20. For them to be common, they need to be compared to another set of multiples.
The first five multiples of 5 are 5, 10, 15, 20 and 25. For them to be common, they need to be compared to another set of multiples.
The common multiples of any two (or more) numbers are multiples of their lowest common multiple (lcm). lcm(9, 11) = 99 → first five common multiples are: 99, 198, 297, 396, 495
The two common multiples of three and five are: 15 and 30 ^-^
They are the first five multiples of their lowest common multiple: 140, 280, 420, 560, 700.