Ben and Albert shared some marbles in the ratio of 5 : 8. After both each gave away 4 marbles to their sister, the ratio of the number of marbles Ben had to the total number of marbles left was 1 : 3. How many marbles did the two boys have in the end?

	Ben	Albert	Difference
Before	5x1 = 5 u	8x1 = 8 u	3x1 = 3 u
Change	- 4	- 4
After	1x3 = 3 u	2x3 = 6 u	1x3 = 3 u

Number of marbles that Ben and Albert each gave to their sister is the same.

The difference in the number of marbles at first and in the end between Ben and Albert remains unchanged.  Make the difference in the number of marbles the same.  LCM of 3 and 1 is 3.

Number of marbles that Ben gave to their sister
= 5 u - 3 u
= 2 u

2 u = 4

1 u = 4 ÷ 2 = 2

Number of marbles that the two boys had in the end
= 3 u + 6 u
= 9 u
= 9 x 2
= 18

Answer(s): 18