Jamie had 25% more erasers than Owen. Isaac had 50% fewer erasers than Jamie. Jamie and Owen gave Isaac some erasers in the ratio of 4 : 5. As a result, Isaac had 60% more erasers than before. Given that Isaac had 50 more erasers than Owen in the end, how many erasers did Jamie give to Isaac?

Jamie	Owen	Isaac
5x2	4x2
2x5		1x5
10	8	5

100% + 25% = 125%
125% = ¹²⁵₁₀₀ = ⁵₄

Jamie : Owen = 5 : 4

100% - 50% = 50%
50% = ⁵⁰₁₀₀ = ¹₂

Jamie : Isaac = 2 : 1

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

	Jamie	Owen	Isaac
Before	10x3 =  30 u	8x3 = 24 u	5x3 = 15 u
Change			+ 3x3 = + 9 u
Comparing the changes in the number of erasers	- 4x1 = - 4 u	- 5x1 = - 5 u	+ 9x1 = + 9 u
After	26 u	19 u	8x3 = 24 u

60% x 5 
= ⁶⁰₁₀₀ x 5 
= 3 

The total number of erasers that Jamie and Owen gave to Isaac is repeated.  Make the total number of erasers that Jamie and Owen gave to Isaac the same.  LCM of 9 and 3 is 9.

Number of erasers that Isaac had more than Owen 
= 24 u - 19 u
= 5 u

5 u = 50

1 u = 50 ÷ 5 = 10

Number of erasers that Jamie gave to Isaac
= 4 u
= 4 x 10
= 40

Answer(s): 40