Ian and Cole shared some erasers in the ratio of 3 : 8. After both each gave away 36 erasers to their sister, the ratio of the number of erasers Ian had to the total number of erasers left was 1 : 5. How many erasers did the two boys have in the end?

	Ian	Cole	Difference
Before	3x3 = 9 u	8x3 = 24 u	5x3 = 15 u
Change	- 36	- 36
After	1x5 = 5 u	4x5 = 20 u	3x5 = 15 u

Number of erasers that Ian and Cole each gave to their sister is the same.

The difference in the number of erasers at first and in the end between Ian and Cole remains unchanged.  Make the difference in the number of erasers the same.  LCM of 5 and 3 is 15.

Number of erasers that Ian gave to their sister
= 9 u - 5 u
= 4 u

4 u = 36

1 u = 36 ÷ 4 = 9

Number of erasers that the two boys had in the end
= 5 u + 20 u
= 25 u
= 25 x 9
= 225

Answer(s): 225