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

	Zoe	Kimberly	Comparing the change in Kimberly's postcards
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 postcards that Kimberly had is repeated.  Make the increase in the number of postcards that Kimberly had the same. LCM of 1 and 3 = 3

3 u = 30

1 u = 30 ÷ 3 = 10

Number of postcards that Kimberly had more than Zoe in the end
= 13 u - 3 u
= 10 u

Number of postcards that Kimberly should give to Zoe so that both had an equal number of postcards in the end
= 10 u ÷ 2
= 5 u
= 5 x 10
= 50

Answer(s): 50