Zara and Joelle collected marbles. Zara gave 30% of her marbles to Joelle and as a result, Joelle's marbles increased by 10%. If Zara had 42 marbles left, find the number of marbles Joelle should give to Zara in the end so that both had an equal number of marbles.

	Zara	Joelle	Comparing the change in Joelle's marbles
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 marbles that Joelle had is repeated.  Make the increase in the number of marbles that Joelle had the same. LCM of 3 and 1 = 3

7 u = 42

1 u = 42 ÷ 7 = 6

Number of marbles that Joelle had more than Zara in the end
= 33 u - 7 u
= 26 u

Number of marbles that Joelle should give to Zara so that both had an equal number of marbles in the end
= 26 u ÷ 2
= 13 u
= 13 x 6
= 78

Answer(s): 78