Tank B contained 3 times as many guppies as Tank C. When 30% of the guppies in Tank B and 20% of the guppies in Tank C were transferred to Tank D, Tank D had 198 guppies, which was 20% more guppies than before. How many less guppies were there in Tank C than Tank B in the end?

	Tank B	Tank C	Tank D
Before	3 u	1 u	5x1.1 = 5.5 u
Change	- 0.9 u	- 0.2 u	+ 1x1.1 = + 1.1 u
After	2.1 u	0.8 u	6x1.1 = 6.6 u

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

Number of guppies that were transferred from Tank C to Tank D
= 20% x 1 u
= ²⁰₁₀₀ x 1 u
= 0.2 u

20% = ²⁰₁₀₀ = ¹₅

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

Total number of guppies transferred from Tank B and Tank C into Tank D
= 0.9 u + 0.2 u
= 1.1 u

6.6 u = 198

1 u = 198 ÷ 6.6 = 30

Number of less guppies in Tank C than Tank B
= 2.1 u - 0.8 u
= 1.3 u
= 1.3 x 30
= 39

Answer(s): 39