Rael had 25% more erasers than Roshel. Tommy had 50% fewer erasers than Rael. Rael and Roshel gave Tommy some erasers in the ratio of 3 : 4. As a result, Tommy had 60% more erasers than before. Given that Roshel had 36 less erasers than Tommy in the end, how many erasers did Roshel give to Tommy?

Rael	Roshel	Tommy
5x2	4x2
2x5		1x5
10	8	5

100% + 25% = 125%
125% = ¹²⁵₁₀₀ = ⁵₄

Rael : Roshel = 5 : 4

100% - 50% = 50%
50% = ⁵⁰₁₀₀ = ¹₂

Rael : Tommy = 2 : 1

The number of erasers that Rael had at first is repeated. Make the number of erasers that Rael had at first the same.  LCM of 5 and 2 is 10.

	Rael	Roshel	Tommy
Before	10x7 =  70 u	8x7 = 56 u	5x7 = 35 u
Change			+ 3x7 = + 21 u
Comparing the changes in the number of erasers	- 3x3 = - 9 u	- 4x3 = - 12 u	+ 7x3 = + 21 u
After	61 u	44 u	8x7 = 56 u

60% x 5 
= ⁶⁰₁₀₀ x 5 
= 3 

The total number of erasers that Rael and Roshel gave to Tommy is repeated.  Make the total number of erasers that Rael and Roshel gave to Tommy the same.  LCM of 7 and 3 is 21.

Number of erasers that Roshel had less than Tommy 
= 56 u - 44 u
= 12 u

12 u = 36

1 u = 36 ÷ 12 = 3

Number of erasers that Roshel gave to Tommy
= 12 u
= 12 x 3
= 36

Answer(s): 36