Tank C contained 4 times as many guppies as Tank D. When 40% of the guppies in Tank C and 20% of the guppies in Tank D were transferred to Tank E, Tank E had 90 guppies, which was 25% more guppies than before. How many more guppies were there in Tank E than Tank D in the end?

	Tank C	Tank D	Tank E
Before	4 u	1 u	4x1.8 = 7.2 u
Change	- 1.6 u	- 0.2 u	+ 1x1.8 = + 1.8 u
After	2.4 u	0.8 u	5x1.8 = 9 u

Number of guppies that were transferred from Tank C to Tank E
= 40% x 4 u
= ⁴⁰₁₀₀ x 4 u
= 1.6 u

Number of guppies that were transferred from Tank D to Tank E
= 20% x 1 u
= ²⁰₁₀₀ x 1 u
= 0.2 u

25% = ²⁵₁₀₀ = ¹₄

Some guppies from Tank C and Tank D were transferred to Tank E.  The total number of guppies transferred from Tank C and Tank D into Tank E is the same.

Total number of guppies transferred from Tank C and Tank D into Tank E
= 1.6 u + 0.2 u
= 1.8 u

9 u = 90

1 u = 90 ÷ 9 = 10

Number of more guppies in Tank E than Tank D
= 9 u - 0.8 u
= 8.2 u
= 8.2 x 10
= 82

Answer(s): 82