Ellie has 2 tanks. Tank B and Tank C are of different capacities. If Tank B is filled by a tap at a rate of 3 litres per minute and Tank C is filled by a tap at a rate of 5 litres per minute, when Tank B is completely filled, 8 litres of water flowed out from Tank C. If Tank B is filled by a tap at a rate of 4 litres per minute and Tank C is filled by a tap at a rate of 2 litres per minute, when Tank B is completely filled, Tank C is only half-filled. What is the capacity of Tank C? Express your answer in litres.

	Scenario 1		Scenario 2
Tank type	Tank B	Tank C	Tank B	Tank C
Volume of the tank	3 u	5 u - 8	4 p	2 p x 2 = 4 p

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

3 u = 4 p --- (1)
5 u - 8 = 4 p
5 u = 4 p + 8 --- (2)

Make u the same.

(1) x 5
15 u = 20 p --- (3)

(2) x 3
15 u = 12 p + 24 --- (4)

(3) = (4)
20 p = 12 p + 24
20 p - 12 p = 24
8 p = 24
1 p = 24 ÷ 8 = 3

Volume of Tank C
= 4 p
= 4 x 3
= 12 ℓ

Answer(s): 12 ℓ