There are some croissants in a box. The croissants can be put into plates of 3 or 9 with no croissants leftover. When the croissants are put into plates of 10, there are short of 5 croissants on the last plate. If there are more than 40 croissants but less than 60 croissants, how many croissants are there in the box?
If croissants can be put into plates of 3 or 9 with no croissants leftover, the number of croissants is a multiple of 9 as 9 is a multiple of 3.

Multiples of 9 that are greater than 40 but less than 60: 45, 54

Multiples of 10 that are greater than 40 but less than 60: 40, 50, 60
Multiples of 10 (- 5) that are greater than 40 but less than 60: 35, 45, 55

Common number = 45

Number of croissants = 45

Answer(s): 45