Joelle and Opal collected stamps. Joelle gave 25% of her stamps to Opal and as a result, Opal's stamps increased by 30%. If Joelle had 81 stamps left, find the number of stamps Opal should give to Joelle in the end so that both had an equal number of stamps.

	Joelle	Opal	Comparing the change in Opal's stamps
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 stamps that Opal had is repeated.  Make the increase in the number of stamps that Opal had the same. LCM of 1 and 3 = 3

9 u = 81

1 u = 81 ÷ 9 = 9

Number of stamps that Opal had more than Joelle in the end
= 13 u - 9 u
= 4 u

Number of stamps that Opal should give to Joelle so that both had an equal number of stamps in the end
= 4 u ÷ 2
= 2 u
= 2 x 9
= 18

Answer(s): 18