Tank E contained 3 times as many guppies as Tank F. When 10% of the guppies in Tank E and 40% of the guppies in Tank F were transferred to Tank G, Tank G had 84 guppies, which was 20% more guppies than before. How many less guppies were there in Tank F than Tank E in the end?

	Tank E	Tank F	Tank G
Before	3 u	1 u	5x0.7 = 3.5 u
Change	- 0.3 u	- 0.4 u	+ 1x0.7 = + 0.7 u
After	2.7 u	0.6 u	6x0.7 = 4.2 u

Number of guppies that were transferred from Tank E to Tank G
= 10% x 3 u
= ¹⁰₁₀₀ x 3 u
= 0.3 u

Number of guppies that were transferred from Tank F to Tank G
= 40% x 1 u
= ⁴⁰₁₀₀ x 1 u
= 0.4 u

20% = ²⁰₁₀₀ = ¹₅

Some guppies from Tank E and Tank F were transferred to Tank G.  The total number of guppies transferred from Tank E and Tank F into Tank G is the same.

Total number of guppies transferred from Tank E and Tank F into Tank G
= 0.3 u + 0.4 u
= 0.7 u

4.2 u = 84

1 u = 84 ÷ 4.2 = 20

Number of less guppies in Tank F than Tank E
= 2.7 u - 0.6 u
= 2.1 u
= 2.1 x 20
= 42

Answer(s): 42