Tank W contained 2 times as many guppies as Tank X. When 30% of the guppies in Tank W and 10% of the guppies in Tank X were transferred to Tank Y, Tank Y had 42 guppies, which was 20% more guppies than before. How many more guppies were there in Tank Y than Tank X in the end?

	Tank W	Tank X	Tank Y
Before	2 u	1 u	5x0.7 = 3.5 u
Change	- 0.6 u	- 0.1 u	+ 1x0.7 = + 0.7 u
After	1.4 u	0.9 u	6x0.7 = 4.2 u

Number of guppies that were transferred from Tank W to Tank Y
= 30% x 2 u
= ³⁰₁₀₀ x 2 u
= 0.6 u

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

20% = ²⁰₁₀₀ = ¹₅

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

Total number of guppies transferred from Tank W and Tank X into Tank Y
= 0.6 u + 0.1 u
= 0.7 u

4.2 u = 42

1 u = 42 ÷ 4.2 = 10

Number of more guppies in Tank Y than Tank X
= 4.2 u - 0.9 u
= 3.3 u
= 3.3 x 10
= 33

Answer(s): 33