In order for a number to be divisible by both 5 and 9, it must be divisible by the least common multiple of 5 and 9, which is 45.

100/45 = 2 2/9, so the smallest 3-digit multiple of 45 is 3*45.

3*45 =

100/45 = 2 2/9, so the smallest 3-digit multiple of 45 is 3*45.

3*45 =

**135**