Sabrina and Nora collected seashells. Sabrina gave 25% of her seashells to Nora and as a result, Nora's seashells increased by 30%. If Sabrina had 81 seashells left, find the number of seashells Nora should give to Sabrina in the end so that both had an equal number of seashells.

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

9 u = 81

1 u = 81 ÷ 9 = 9

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

Number of seashells that Nora should give to Sabrina so that both had an equal number of seashells in the end
= 4 u ÷ 2
= 2 u
= 2 x 9
= 18

Answer(s): 18