The largest common multiple is an infinite number and not very practical.
The GCF is 15.
The LCM is 300.
The multiples of 15 are 15, 30, 45, 60, 75 and so on. For them to be common, they need to be compared to another set of multiples.
Since the lowest common multiple of 3 and 5 is 15, the common multiples of 3 and 5 are the multiples of 15: 30, 45, 60, 75, 90, etc...
Since 75 is a multiple of 25, all of its multiples are common.
The common multiples of 3 and 15 from 1 to 100 are 15, 30, 45, 60, 75, and 90.
The common multiples of 3 and 15 from 1 to 100 are 15, 30, 45, 60, 75, 90
15, 30, 45, 60, 75, 90
The multiples of 20 are 20, 40, 60, 80, 100, 120... The multiples of 30 are 30, 60, 90, 120, 150... The multiples of 15 are 15, 30, 45, 60, 75, 90, 105, 120, 135... The common multiples of 20, 30, and 15 are 60, 120, 180, 240...
15, 30, 45, 60, 75, 90
15, 30, 45, 60, 75, 90.
15, 30, 45, 60, 75, 90
15, 30, 45, 60, 75, 90
15, 30, 45, 60, 75, 90