Tank C contained 2 times as many guppies as Tank D. When 40% of the guppies in Tank C and 10% of the guppies in Tank D were transferred to Tank E, Tank E had 216 guppies, which was 20% more guppies than before. How many more guppies were there in Tank E than Tank D in the end?

	Tank C	Tank D	Tank E
Before	2 u	1 u	5x0.9 = 4.5 u
Change	- 0.8 u	- 0.1 u	+ 1x0.9 = + 0.9 u
After	1.2 u	0.9 u	6x0.9 = 5.4 u

Number of guppies that were transferred from Tank C to Tank E
= 40% x 2 u
= ⁴⁰₁₀₀ x 2 u
= 0.8 u

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

20% = ²⁰₁₀₀ = ¹₅

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

Total number of guppies transferred from Tank C and Tank D into Tank E
= 0.8 u + 0.1 u
= 0.9 u

5.4 u = 216

1 u = 216 ÷ 5.4 = 40

Number of more guppies in Tank E than Tank D
= 5.4 u - 0.9 u
= 4.5 u
= 4.5 x 40
= 180

Answer(s): 180