Gwen and Tiffany collected postcards. Gwen gave 60% of her postcards to Tiffany and as a result, Tiffany's postcards increased by 20%. If Gwen had 12 postcards left, find the number of postcards Tiffany should give to Gwen in the end so that both had an equal number of postcards.

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

2 u = 12

1 u = 12 ÷ 2 = 6

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

Number of postcards that Tiffany should give to Gwen so that both had an equal number of postcards in the end
= 16 u ÷ 2
= 8 u
= 8 x 6
= 48

Answer(s): 48