Tank R contained 4 times as many guppies as Tank S. When 30% of the guppies in Tank R and 20% of the guppies in Tank S were transferred to Tank T, Tank T had 84 guppies, which was 50% more guppies than before. How many less guppies were there in Tank S than Tank R in the end?

	Tank R	Tank S	Tank T
Before	4 u	1 u	2x1.4 = 2.8 u
Change	- 1.2 u	- 0.2 u	+ 1x1.4 = + 1.4 u
After	2.8 u	0.8 u	3x1.4 = 4.2 u

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

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

50% = ⁵⁰₁₀₀ = ¹₂

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

Total number of guppies transferred from Tank R and Tank S into Tank T
= 1.2 u + 0.2 u
= 1.4 u

4.2 u = 84

1 u = 84 ÷ 4.2 = 20

Number of less guppies in Tank S than Tank R
= 2.8 u - 0.8 u
= 2 u
= 2 x 20
= 40

Answer(s): 40