Ivory and Mary collected seashells. Ivory gave 25% of her seashells to Mary and as a result, Mary's seashells increased by 30%. If Ivory had 99 seashells left, find the number of seashells Mary should give to Ivory in the end so that both had an equal number of seashells.

	Ivory	Mary	Comparing the change in Mary's seashells
Before	4x3 = 12 u		10x1 = 10u
Change	- 1x3 = - 3 u	+ 1x3 = + 3 u	+ 3x1 = + 3 u
After	3x3 = 9 u		13x1 = 13 u

25% = ²⁵₁₀₀ = ¹₄
30% = ³⁰₁₀₀ = ³₁₀

The increase in the number of seashells that Mary had is repeated.  Make the increase in the number of seashells that Mary had the same. LCM of 1 and 3 = 3

9 u = 99

1 u = 99 ÷ 9 = 11

Number of seashells that Mary had more than Ivory in the end
= 13 u - 9 u
= 4 u

Number of seashells that Mary should give to Ivory so that both had an equal number of seashells in the end
= 4 u ÷ 2
= 2 u
= 2 x 11
= 22

Answer(s): 22