There are some tarts in a box. The tarts can be put into plates of 5 or 10 with no tarts leftover. When the tarts are put into plates of 6, there are short of 4 tarts on the last plate. If there are more than 40 tarts but less than 60 tarts, how many tarts are there in the box?
If tarts can be put into plates of 5 or 10 with no tarts leftover, the number of tarts is a multiple of 10 as 10 is a multiple of 5.

Multiples of 10 that are greater than 40 but less than 60: 40, 50, 60

Multiples of 6 that are greater than 40 but less than 60: 42, 48, 54, 60
Multiples of 6 (- 4) that are greater than 40 but less than 60: 38, 44, 50, 56

Common number = 50

Number of tarts = 50

Answer(s): 50