Tank D contained 4 times as many guppies as Tank E. When 10% of the guppies in Tank D and 40% of the guppies in Tank E were transferred to Tank F, Tank F had 160 guppies, which was 25% more guppies than before. How many less guppies were there in Tank E than Tank D in the end?

	Tank D	Tank E	Tank F
Before	4 u	1 u	4x0.8 = 3.2 u
Change	- 0.4 u	- 0.4 u	+ 1x0.8 = + 0.8 u
After	3.6 u	0.6 u	5x0.8 = 4 u

Number of guppies that were transferred from Tank D to Tank F
= 10% x 4 u
= ¹⁰₁₀₀ x 4 u
= 0.4 u

Number of guppies that were transferred from Tank E to Tank F
= 40% x 1 u
= ⁴⁰₁₀₀ x 1 u
= 0.4 u

25% = ²⁵₁₀₀ = ¹₄

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

Total number of guppies transferred from Tank D and Tank E into Tank F
= 0.4 u + 0.4 u
= 0.8 u

4 u = 160

1 u = 160 ÷ 4 = 40

Number of less guppies in Tank E than Tank D
= 3.6 u - 0.6 u
= 3 u
= 3 x 40
= 120

Answer(s): 120