Tank F contained 4 times as many guppies as Tank G. When 50% of the guppies in Tank F and 10% of the guppies in Tank G were transferred to Tank H, Tank H had 420 guppies, which was 25% more guppies than before. How many more guppies were there in Tank H than Tank G in the end?

	Tank F	Tank G	Tank H
Before	4 u	1 u	4x2.1 = 8.4 u
Change	- 2 u	- 0.1 u	+ 1x2.1 = + 2.1 u
After	2 u	0.9 u	5x2.1 = 10.5 u

Number of guppies that were transferred from Tank F to Tank H
= 50% x 4 u
= ⁵⁰₁₀₀ x 4 u
= 2 u

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

25% = ²⁵₁₀₀ = ¹₄

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

Total number of guppies transferred from Tank F and Tank G into Tank H
= 2 u + 0.1 u
= 2.1 u

10.5 u = 420

1 u = 420 ÷ 10.5 = 40

Number of more guppies in Tank H than Tank G
= 10.5 u - 0.9 u
= 9.6 u
= 9.6 x 40
= 384

Answer(s): 384