Tank V contained 4 times as many guppies as Tank W. When 30% of the guppies in Tank V and 20% of the guppies in Tank W were transferred to Tank X, Tank X had 84 guppies, which was 20% more guppies than before. How many less guppies were there in Tank W than Tank V in the end?

	Tank V	Tank W	Tank X
Before	4 u	1 u	5x1.4 = 7 u
Change	- 1.2 u	- 0.2 u	+ 1x1.4 = + 1.4 u
After	2.8 u	0.8 u	6x1.4 = 8.4 u

Number of guppies that were transferred from Tank V to Tank X
= 30% x 4 u
= ³⁰₁₀₀ x 4 u
= 1.2 u

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

20% = ²⁰₁₀₀ = ¹₅

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

Total number of guppies transferred from Tank V and Tank W into Tank X
= 1.2 u + 0.2 u
= 1.4 u

8.4 u = 84

1 u = 84 ÷ 8.4 = 10

Number of less guppies in Tank W than Tank V
= 2.8 u - 0.8 u
= 2 u
= 2 x 10
= 20

Answer(s): 20