Tank C contained 4 times as many guppies as Tank D. When 30% of the guppies in Tank C and 10% of the guppies in Tank D were transferred to Tank E, Tank E had 117 guppies, which was 50% 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	4 u	1 u	2x1.3 = 2.6 u
Change	- 1.2 u	- 0.1 u	+ 1x1.3 = + 1.3 u
After	2.8 u	0.9 u	3x1.3 = 3.9 u

Number of guppies that were transferred from Tank C to Tank E
= 30% x 4 u
= ³⁰₁₀₀ x 4 u
= 1.2 u

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

50% = ⁵⁰₁₀₀ = ¹₂

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
= 1.2 u + 0.1 u
= 1.3 u

3.9 u = 117

1 u = 117 ÷ 3.9 = 30

Number of more guppies in Tank E than Tank D
= 3.9 u - 0.9 u
= 3 u
= 3 x 30
= 90

Answer(s): 90