Tank K contained 3 times as many guppies as Tank L. When 10% of the guppies in Tank K and 30% of the guppies in Tank L were transferred to Tank M, Tank M had 60 guppies, which was 25% more guppies than before. How many less guppies were there in Tank L than Tank K in the end?

	Tank K	Tank L	Tank M
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 K to Tank M
= 10% x 3 u
= ¹⁰₁₀₀ x 3 u
= 0.3 u

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

25% = ²⁵₁₀₀ = ¹₄

Some guppies from Tank K and Tank L were transferred to Tank M.  The total number of guppies transferred from Tank K and Tank L into Tank M is the same.

Total number of guppies transferred from Tank K and Tank L into Tank M
= 0.3 u + 0.3 u
= 0.6 u

3 u = 60

1 u = 60 ÷ 3 = 20

Number of less guppies in Tank L than Tank K
= 2.7 u - 0.7 u
= 2 u
= 2 x 20
= 40

Answer(s): 40