Tank U contained 4 times as many guppies as Tank V. When 10% of the guppies in Tank U and 20% of the guppies in Tank V were transferred to Tank W, Tank W had 72 guppies, which was 20% more guppies than before. How many less guppies were there in Tank V than Tank U in the end?

	Tank U	Tank V	Tank W
Before	4 u	1 u	5x0.6 = 3 u
Change	- 0.4 u	- 0.2 u	+ 1x0.6 = + 0.6 u
After	3.6 u	0.8 u	6x0.6 = 3.6 u

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

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

20% = ²⁰₁₀₀ = ¹₅

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

Total number of guppies transferred from Tank U and Tank V into Tank W
= 0.4 u + 0.2 u
= 0.6 u

3.6 u = 72

1 u = 72 ÷ 3.6 = 20

Number of less guppies in Tank V than Tank U
= 3.6 u - 0.8 u
= 2.8 u
= 2.8 x 20
= 56

Answer(s): 56