They are: 3*5*7*8 = 840, except they are factors.
Multiples are numbers that a number (840 in this case) is a factor of.Multiples of 840: 1680, 2520, 3360, and so on.
The common multiples of 4, 5, 7, and 15 are 420, 840, 1260 and so on.
840
All multiples of 840 are common multiples of 60 and 280
For all natural numbers ( the counting numbers, 1,2,3,4, are natural numbers), 840 times each of those is a multiple of 840. We say let k be the natural numbers 1,2,3... where ... means it goes on forever. So we have 840k are all the multiples Here is a list of a few. 840 x 1 = 840 840 x 2 = 1680 840 x 3 = 2520 840 x 4 = 3360 we continue with 840x5, 840x6, etc.
Multiples of 840
840
That's an infinite list.
Any multiple of 4200
Any multiple of 840.
Any multiple of 42000
420, 840, 1260, 1680, 2100, 2520 +420 . . .