Dana and Risa collected postcards. Dana gave 60% of her postcards to Risa and as a result, Risa's postcards increased by 20%. If Dana had 24 postcards left, find the number of postcards Risa should give to Dana in the end so that both had an equal number of postcards.

	Dana	Risa	Comparing the change in Risa's postcards
Before	5x1 = 5 u		5x3 = 15u
Change	- 3x1 = - 3 u	+ 3x1 = + 3 u	+ 1x3 = + 3 u
After	2x1 = 2 u		6x3 = 18 u

60% = ⁶⁰₁₀₀ = ³₅
20% = ²⁰₁₀₀ = ¹₅

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

2 u = 24

1 u = 24 ÷ 2 = 12

Number of postcards that Risa had more than Dana in the end
= 18 u - 2 u
= 16 u

Number of postcards that Risa should give to Dana so that both had an equal number of postcards in the end
= 16 u ÷ 2
= 8 u
= 8 x 12
= 96

Answer(s): 96