Tank G contained 3 times as many guppies as Tank H. When 30% of the guppies in Tank G and 40% of the guppies in Tank H were transferred to Tank J, Tank J had 78 guppies, which was 20% more guppies than before. How many less guppies were there in Tank H than Tank G in the end?

	Tank G	Tank H	Tank J
Before	3 u	1 u	5x1.3 = 6.5 u
Change	- 0.9 u	- 0.4 u	+ 1x1.3 = + 1.3 u
After	2.1 u	0.6 u	6x1.3 = 7.8 u

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

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

20% = ²⁰₁₀₀ = ¹₅

Some guppies from Tank G and Tank H were transferred to Tank J.  The total number of guppies transferred from Tank G and Tank H into Tank J is the same.

Total number of guppies transferred from Tank G and Tank H into Tank J
= 0.9 u + 0.4 u
= 1.3 u

7.8 u = 78

1 u = 78 ÷ 7.8 = 10

Number of less guppies in Tank H than Tank G
= 2.1 u - 0.6 u
= 1.5 u
= 1.5 x 10
= 15

Answer(s): 15