Tank L contained 3 times as many guppies as Tank M. When 30% of the guppies in Tank L and 10% of the guppies in Tank M were transferred to Tank N, Tank N had 60 guppies, which was 20% more guppies than before. How many less guppies were there in Tank M than Tank L in the end?

	Tank L	Tank M	Tank N
Before	3 u	1 u	5x1 = 5 u
Change	- 0.9 u	- 0.1 u	+ 1x1 = + 1 u
After	2.1 u	0.9 u	6x1 = 6 u

Number of guppies that were transferred from Tank L to Tank N
= 30% x 3 u
= ³⁰₁₀₀ x 3 u
= 0.9 u

Number of guppies that were transferred from Tank M to Tank N
= 10% x 1 u
= ¹⁰₁₀₀ x 1 u
= 0.1 u

20% = ²⁰₁₀₀ = ¹₅

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

Total number of guppies transferred from Tank L and Tank M into Tank N
= 0.9 u + 0.1 u
= 1 u

6 u = 60

1 u = 60 ÷ 6 = 10

Number of less guppies in Tank M than Tank L
= 2.1 u - 0.9 u
= 1.2 u
= 1.2 x 10
= 12

Answer(s): 12