Question

Which minimum number should be added to 15, to make it a multiple of both 3 and 6?

Answer 1

Multiples of 3: 3, 6, 9, 12, 15, 18, 21, 24...
Multiples of 6: 6, 12, 18, 24, 30...

Common Multiples of 3 and 6 are: 6, 12, 18, 24, 30

The minimum number which can be added to 15 to get a common multiple of 3 and 6 will be: 18 - 15 = 3

Hence by adding 3 to 15, we will get 18, a multiple of both 3 and 5.