Rael has 2 tanks. Tank C and Tank D are of different capacities. If Tank C is filled by a tap at a rate of 3 litres per minute and Tank D is filled by a tap at a rate of 7 litres per minute, when Tank C is completely filled, 8 litres of water flowed out from Tank D. If Tank C is filled by a tap at a rate of 5 litres per minute and Tank D is filled by a tap at a rate of 5 litres per minute, when Tank C is completely filled, Tank D is only half-filled. What is the capacity of Tank D? Express your answer in litres.

	Scenario 1		Scenario 2
Tank type	Tank C	Tank D	Tank C	Tank D
Volume of the tank	3 u	7 u - 8	5 p	5 p x 2 = 10 p

Let 1 u be the time taken for Scenario 1.
Let 1 p be the time taken for Scenario 2.

3 u = 5 p --- (1)
7 u - 8 = 10 p
7 u = 10 p + 8 --- (2)

Make u the same.

(1) x 7
21 u = 35 p --- (3)

(2) x 3
21 u = 30 p + 24 --- (4)

(3) = (4)
35 p = 30 p + 24
35 p - 30 p = 24
5 p = 24
1 p = 24 ÷ 5 = 4.8

Volume of Tank D
= 10 p
= 10 x 4.8
= 48 ℓ

Answer(s): 48 ℓ