There are some puffs in a box. The puffs can be put into plates of 3 or 9 with no puffs leftover. When the puffs are put into plates of 6, there are short of 3 puffs on the last plate. If there are more than 30 puffs but less than 50 puffs, how many puffs are there in the box?
If puffs can be put into plates of 3 or 9 with no puffs leftover, the number of puffs is a multiple of 9 as 9 is a multiple of 3.

Multiples of 9 that are greater than 30 but less than 50: 36, 45

Multiples of 6 that are greater than 30 but less than 50: 30, 36, 42, 48
Multiples of 6 (- 3) that are greater than 30 but less than 50: 27, 33, 39, 45

Common number = 45

Number of puffs = 45

Answer(s): 45