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

	Yen	Cathy	Comparing the change in Cathy's seashells
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 seashells that Cathy had is repeated.  Make the increase in the number of seashells that Cathy had the same. LCM of 3 and 1 = 3

7 u = 42

1 u = 42 ÷ 7 = 6

Number of seashells that Cathy had more than Yen in the end
= 33 u - 7 u
= 26 u

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

Answer(s): 78