Min and Olivia collected erasers. Min gave 25% of her erasers to Olivia and as a result, Olivia's erasers increased by 30%. If Min had 90 erasers left, find the number of erasers Olivia should give to Min in the end so that both had an equal number of erasers.

	Min	Olivia	Comparing the change in Olivia's erasers
Before	4x3 = 12 u		10x1 = 10u
Change	- 1x3 = - 3 u	+ 1x3 = + 3 u	+ 3x1 = + 3 u
After	3x3 = 9 u		13x1 = 13 u

25% = ²⁵₁₀₀ = ¹₄
30% = ³⁰₁₀₀ = ³₁₀

The increase in the number of erasers that Olivia had is repeated.  Make the increase in the number of erasers that Olivia had the same. LCM of 1 and 3 = 3

9 u = 90

1 u = 90 ÷ 9 = 10

Number of erasers that Olivia had more than Min in the end
= 13 u - 9 u
= 4 u

Number of erasers that Olivia should give to Min so that both had an equal number of erasers in the end
= 4 u ÷ 2
= 2 u
= 2 x 10
= 20

Answer(s): 20