Tank A contained 3 times as many guppies as Tank B. When 10% of the guppies in Tank A and 30% of the guppies in Tank B were transferred to Tank C, Tank C had 30 guppies, which was 25% more guppies than before. How many less guppies were there in Tank B than Tank A in the end?

	Tank A	Tank B	Tank C
Before	3 u	1 u	4x0.6 = 2.4 u
Change	- 0.3 u	- 0.3 u	+ 1x0.6 = + 0.6 u
After	2.7 u	0.7 u	5x0.6 = 3 u

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

Number of guppies that were transferred from Tank B to Tank C
= 30% x 1 u
= ³⁰₁₀₀ x 1 u
= 0.3 u

25% = ²⁵₁₀₀ = ¹₄

Some guppies from Tank A and Tank B were transferred to Tank C.  The total number of guppies transferred from Tank A and Tank B into Tank C is the same.

Total number of guppies transferred from Tank A and Tank B into Tank C
= 0.3 u + 0.3 u
= 0.6 u

3 u = 30

1 u = 30 ÷ 3 = 10

Number of less guppies in Tank B than Tank A
= 2.7 u - 0.7 u
= 2 u
= 2 x 10
= 20

Answer(s): 20