Tank X contained 4 times as many guppies as Tank Y. When 40% of the guppies in Tank X and 10% of the guppies in Tank Y were transferred to Tank Z, Tank Z had 170 guppies, which was 25% more guppies than before. How many more guppies were there in Tank Z than Tank Y in the end?

	Tank X	Tank Y	Tank Z
Before	4 u	1 u	4x1.7 = 6.8 u
Change	- 1.6 u	- 0.1 u	+ 1x1.7 = + 1.7 u
After	2.4 u	0.9 u	5x1.7 = 8.5 u

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

Number of guppies that were transferred from Tank Y to Tank Z
= 10% x 1 u
= ¹⁰₁₀₀ x 1 u
= 0.1 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
= 1.6 u + 0.1 u
= 1.7 u

8.5 u = 170

1 u = 170 ÷ 8.5 = 20

Number of more guppies in Tank Z than Tank Y
= 8.5 u - 0.9 u
= 7.6 u
= 7.6 x 20
= 152

Answer(s): 152