Kimberly and Xandra collected postcards. Kimberly gave 30% of her postcards to Xandra and as a result, Xandra's postcards increased by 10%. If Kimberly had 84 postcards left, find the number of postcards Xandra should give to Kimberly in the end so that both had an equal number of postcards.

	Kimberly	Xandra	Comparing the change in Xandra's postcards
Before	10x1 = 10 u		10x3 = 30u
Change	- 3x1 = - 3 u	+ 3x1 = + 3 u	+ 1x3 = + 3 u
After	7x1 = 7 u		11x3 = 33 u

30% = ³⁰₁₀₀ = ³₁₀
10% = ¹⁰₁₀₀ = ¹₁₀

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

7 u = 84

1 u = 84 ÷ 7 = 12

Number of postcards that Xandra had more than Kimberly in the end
= 33 u - 7 u
= 26 u

Number of postcards that Xandra should give to Kimberly so that both had an equal number of postcards in the end
= 26 u ÷ 2
= 13 u
= 13 x 12
= 156

Answer(s): 156