Tank P contained 4 times as many guppies as Tank Q. When 10% of the guppies in Tank P and 10% of the guppies in Tank Q were transferred to Tank R, Tank R had 120 guppies, which was 20% more guppies than before. How many less guppies were there in Tank Q than Tank P in the end?

	Tank P	Tank Q	Tank R
Before	4 u	1 u	5x0.5 = 2.5 u
Change	- 0.4 u	- 0.1 u	+ 1x0.5 = + 0.5 u
After	3.6 u	0.9 u	6x0.5 = 3 u

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

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

20% = ²⁰₁₀₀ = ¹₅

Some guppies from Tank P and Tank Q were transferred to Tank R.  The total number of guppies transferred from Tank P and Tank Q into Tank R is the same.

Total number of guppies transferred from Tank P and Tank Q into Tank R
= 0.4 u + 0.1 u
= 0.5 u

3 u = 120

1 u = 120 ÷ 3 = 40

Number of less guppies in Tank Q than Tank P
= 3.6 u - 0.9 u
= 2.7 u
= 2.7 x 40
= 108

Answer(s): 108