Xuan and Anna collected postcards. Xuan gave 30% of her postcards to Anna and as a result, Anna's postcards increased by 10%. If Xuan had 70 postcards left, find the number of postcards Anna should give to Xuan in the end so that both had an equal number of postcards.

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

7 u = 70

1 u = 70 ÷ 7 = 10

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

Number of postcards that Anna should give to Xuan so that both had an equal number of postcards in the end
= 26 u ÷ 2
= 13 u
= 13 x 10
= 130

Answer(s): 130