Carl and Luis shared some coins in the ratio of 3 : 8. After both each gave away 42 coins to their cousin, the ratio of the number of coins Carl had to the total number of coins left was 1 : 6. How many coins did the two boys have in the end?

	Carl	Luis	Difference
Before	3x4 = 12 u	8x4 = 32 u	5x4 = 20 u
Change	- 42	- 42
After	1x5 = 5 u	5x5 = 25 u	4x5 = 20 u

Number of coins that Carl and Luis each gave to their cousin is the same.

The difference in the number of coins at first and in the end between Carl and Luis remains unchanged.  Make the difference in the number of coins the same.  LCM of 5 and 4 is 20.

Number of coins that Carl gave to their cousin
= 12 u - 5 u
= 7 u

7 u = 42

1 u = 42 ÷ 7 = 6

Number of coins that the two boys had in the end
= 5 u + 25 u
= 30 u
= 30 x 6
= 180

Answer(s): 180