Tank S contained 4 times as many guppies as Tank T. When 20% of the guppies in Tank S and 10% of the guppies in Tank T were transferred to Tank U, Tank U had 108 guppies, which was 20% more guppies than before. How many less guppies were there in Tank T than Tank S in the end?

	Tank S	Tank T	Tank U
Before	4 u	1 u	5x0.9 = 4.5 u
Change	- 0.8 u	- 0.1 u	+ 1x0.9 = + 0.9 u
After	3.2 u	0.9 u	6x0.9 = 5.4 u

Number of guppies that were transferred from Tank S to Tank U
= 20% x 4 u
= ²⁰₁₀₀ x 4 u
= 0.8 u

Number of guppies that were transferred from Tank T to Tank U
= 10% x 1 u
= ¹⁰₁₀₀ x 1 u
= 0.1 u

20% = ²⁰₁₀₀ = ¹₅

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 + 0.1 u
= 0.9 u

5.4 u = 108

1 u = 108 ÷ 5.4 = 20

Number of less guppies in Tank T than Tank S
= 3.2 u - 0.9 u
= 2.3 u
= 2.3 x 20
= 46

Answer(s): 46