Cody, Ahmad and Michael have some erasers. The ratios of their erasers are as follows:

Cody : (Cody + Ahmad + Michael) = 1 : 4
Ahmad : (Cody + Michael) = 1 : 5

Michael has 15 erasers more than Ahmad. In the end, Michael gives away all he has to Ahmad and Cody so that both Ahmad and Cody end up with the same number of erasers, how many erasers has Ahmad received from Michael?

Ahmad	Michael	Cody	Total
3x3		1x3	4x3
1x2	5x2		6x2
2 u	7 u	3 u	12 u

The total number of erasers is repeated.  Make the total number of erasers the same.  LCM of 4 and 6 is 12.

Number of erasers that Michael has more than Ahmad
= 7 u - 2 u
= 5 u

5 u = 15

1 u = 15 ÷ 5 = 3

	Ahmad	Michael	Cody
Before	2 u	7 u	3 u
Change	+ 4 u	- 7 u	+ 3 u
After	6 u	0 u	6 u

Number of erasers that Ahmad has received from Michael
= 6 u - 2 u 
= 4 u
= 4 x 3
= 12

Answer(s): 12