Tank X contained 3 times as many guppies as Tank Y. When 20% of the guppies in Tank X and 20% of the guppies in Tank Y were transferred to Tank Z, Tank Z had 80 guppies, which was 25% more guppies than before. How many less guppies were there in Tank Y than Tank X in the end?

	Tank X	Tank Y	Tank Z
Before	3 u	1 u	4x0.8 = 3.2 u
Change	- 0.6 u	- 0.2 u	+ 1x0.8 = + 0.8 u
After	2.4 u	0.8 u	5x0.8 = 4 u

Number of guppies that were transferred from Tank X to Tank Z
= 20% x 3 u
= ²⁰₁₀₀ x 3 u
= 0.6 u

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

25% = ²⁵₁₀₀ = ¹₄

Some guppies from Tank X and Tank Y were transferred to Tank Z.  The total number of guppies transferred from Tank X and Tank Y into Tank Z is the same.

Total number of guppies transferred from Tank X and Tank Y into Tank Z
= 0.6 u + 0.2 u
= 0.8 u

4 u = 80

1 u = 80 ÷ 4 = 20

Number of less guppies in Tank Y than Tank X
= 2.4 u - 0.8 u
= 1.6 u
= 1.6 x 20
= 32

Answer(s): 32