Tank S contained 2 times as many guppies as Tank T. When 40% of the guppies in Tank S and 20% of the guppies in Tank T were transferred to Tank U, Tank U had 50 guppies, which was 25% more guppies than before. How many more guppies were there in Tank U than Tank T in the end?

	Tank S	Tank T	Tank U
Before	2 u	1 u	4x1 = 4 u
Change	- 0.8 u	- 0.2 u	+ 1x1 = + 1 u
After	1.2 u	0.8 u	5x1 = 5 u

Number of guppies that were transferred from Tank S to Tank U
= 40% x 2 u
= ⁴⁰₁₀₀ x 2 u
= 0.8 u

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

25% = ²⁵₁₀₀ = ¹₄

Some guppies from Tank S and Tank T were transferred to Tank U.  The total number of guppies transferred from Tank S and Tank T into Tank U is the same.

Total number of guppies transferred from Tank S and Tank T into Tank U
= 0.8 u + 0.2 u
= 1 u

5 u = 50

1 u = 50 ÷ 5 = 10

Number of more guppies in Tank U than Tank T
= 5 u - 0.8 u
= 4.2 u
= 4.2 x 10
= 42

Answer(s): 42