42 is the LCM of 3, 6 and 7. All multiples of 42 are multiples of 3, 6 and 7
The common multiples of an set of numbers are the multiples of their lowest common multiple. lcm(7, 8, 9) = 504 → the first 3 common multiples of 7, 8, 9 are 504, 1008, 1512.
1,7
There are infinitely many common multiples of 3, 5 and 7, each one 105 larger than the previous one. Or to put it another way: the common multiples of 3, 5 and 7 are the multiples of their lowest common multiple which is 105. ie their common multiples are all the multiples of 105, of which there is no end - there is an infinite number of multiples of 105 (or any other number [except zero]).
It is: 42
42
455
56
35 7x5
The common multiples of 3 and 7 are 21, 42, 63 and so on.
The LCM is: 168
The lowest common multiple of 7 and 9 is 63. The common multiples of 7 and 9 are therefore the infinite set of multiples of 63. Thus, the common multiples of 7 and 9 are 63, 126, 189, 252, 315, 378, 441, 504, 567, 630, 693, and so on.