Tank A contained 2 times as many guppies as Tank B. When 10% of the guppies in Tank A and 40% of the guppies in Tank B were transferred to Tank C, Tank C had 72 guppies, which was 20% 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	2 u	1 u	5x0.6 = 3 u
Change	- 0.2 u	- 0.4 u	+ 1x0.6 = + 0.6 u
After	1.8 u	0.6 u	6x0.6 = 3.6 u

Number of guppies that were transferred from Tank A to Tank C
= 10% x 2 u
= ¹⁰₁₀₀ x 2 u
= 0.2 u

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

20% = ²⁰₁₀₀ = ¹₅

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
= 0.2 u + 0.4 u
= 0.6 u

3.6 u = 72

1 u = 72 ÷ 3.6 = 20

Number of less guppies in Tank B than Tank A
= 1.8 u - 0.6 u
= 1.2 u
= 1.2 x 20
= 24

Answer(s): 24