Sarah and Gabby collected stickers. Sarah gave 50% of her stickers to Gabby and as a result, Gabby's stickers increased by 30%. If Sarah had 21 stickers left, find the number of stickers Gabby should give to Sarah in the end so that both had an equal number of stickers.

	Sarah	Gabby	Comparing the change in Gabby's stickers
Before	2x3 = 6 u		10x1 = 10u
Change	- 1x3 = - 3 u	+ 1x3 = + 3 u	+ 3x1 = + 3 u
After	1x3 = 3 u		13x1 = 13 u

50% = ⁵⁰₁₀₀ = ¹₂
30% = ³⁰₁₀₀ = ³₁₀

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

3 u = 21

1 u = 21 ÷ 3 = 7

Number of stickers that Gabby had more than Sarah in the end
= 13 u - 3 u
= 10 u

Number of stickers that Gabby should give to Sarah so that both had an equal number of stickers in the end
= 10 u ÷ 2
= 5 u
= 5 x 7
= 35

Answer(s): 35