Tank Q contained 3 times as many guppies as Tank R. When 10% of the guppies in Tank Q and 40% of the guppies in Tank R were transferred to Tank S, Tank S had 140 guppies, which was 25% more guppies than before. How many less guppies were there in Tank R than Tank Q in the end?

	Tank Q	Tank R	Tank S
Before	3 u	1 u	4x0.7 = 2.8 u
Change	- 0.3 u	- 0.4 u	+ 1x0.7 = + 0.7 u
After	2.7 u	0.6 u	5x0.7 = 3.5 u

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

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

25% = ²⁵₁₀₀ = ¹₄

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

Total number of guppies transferred from Tank Q and Tank R into Tank S
= 0.3 u + 0.4 u
= 0.7 u

3.5 u = 140

1 u = 140 ÷ 3.5 = 40

Number of less guppies in Tank R than Tank Q
= 2.7 u - 0.6 u
= 2.1 u
= 2.1 x 40
= 84

Answer(s): 84