#### Answer

30

#### Work Step by Step

6, 3, 5, 15
First let's note down the multiples of each.
We do not need to find multiple of 3 and 5 as
6 & 15 are the multiple of 3 and
15 is multiple of 15
Multiples of 6 : 6, 12, 18, 24, 30, 36,..
Multiples of 15 : 15, 30, 45, 60, 75, 90,..
Looking at the above, 30 is the least common multiple of 6, 3, 5, 15.