Tank M contained 3 times as many guppies as Tank N. When 40% of the guppies in Tank M and 30% of the guppies in Tank N were transferred to Tank P, Tank P had 90 guppies, which was 20% more guppies than before. How many more guppies were there in Tank P than Tank N in the end?

	Tank M	Tank N	Tank P
Before	3 u	1 u	5x1.5 = 7.5 u
Change	- 1.2 u	- 0.3 u	+ 1x1.5 = + 1.5 u
After	1.8 u	0.7 u	6x1.5 = 9 u

Number of guppies that were transferred from Tank M to Tank P
= 40% x 3 u
= ⁴⁰₁₀₀ x 3 u
= 1.2 u

Number of guppies that were transferred from Tank N to Tank P
= 30% x 1 u
= ³⁰₁₀₀ x 1 u
= 0.3 u

20% = ²⁰₁₀₀ = ¹₅

Some guppies from Tank M and Tank N were transferred to Tank P.  The total number of guppies transferred from Tank M and Tank N into Tank P is the same.

Total number of guppies transferred from Tank M and Tank N into Tank P
= 1.2 u + 0.3 u
= 1.5 u

9 u = 90

1 u = 90 ÷ 9 = 10

Number of more guppies in Tank P than Tank N
= 9 u - 0.7 u
= 8.3 u
= 8.3 x 10
= 83

Answer(s): 83