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

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

3 u = 30

1 u = 30 ÷ 3 = 10

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

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

Answer(s): 50