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

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

3 u = 21

1 u = 21 ÷ 3 = 7

Number of seashells that Ivory had more than Lucy in the end
= 13 u - 3 u
= 10 u

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

Answer(s): 35