Nicole and Min collected postcards. Nicole gave 50% of her postcards to Min and as a result, Min's postcards increased by 30%. If Nicole had 21 postcards left, find the number of postcards Min should give to Nicole in the end so that both had an equal number of postcards.

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

3 u = 21

1 u = 21 ÷ 3 = 7

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

Number of postcards that Min should give to Nicole so that both had an equal number of postcards in the end
= 10 u ÷ 2
= 5 u
= 5 x 7
= 35

Answer(s): 35