Lucy and Fanny collected postcards. Lucy gave 30% of her postcards to Fanny and as a result, Fanny's postcards increased by 10%. If Lucy had 77 postcards left, find the number of postcards Fanny should give to Lucy in the end so that both had an equal number of postcards.

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

7 u = 77

1 u = 77 ÷ 7 = 11

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

Number of postcards that Fanny should give to Lucy so that both had an equal number of postcards in the end
= 26 u ÷ 2
= 13 u
= 13 x 11
= 143

Answer(s): 143