Gabriel has 2 tanks. Tank Q and Tank R are of different capacities. If Tank Q is filled by a tap at a rate of 5 litres per minute and Tank R is filled by a tap at a rate of 6 litres per minute, when Tank Q is completely filled, 5 litres of water flowed out from Tank R. If Tank Q is filled by a tap at a rate of 5 litres per minute and Tank R is filled by a tap at a rate of 2 litres per minute, when Tank Q is completely filled, Tank R is only half-filled. What is the capacity of Tank R? Express your answer in litres.

	Scenario 1		Scenario 2
Tank type	Tank Q	Tank R	Tank Q	Tank R
Volume of the tank	5 u	6 u - 5	5 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.

5 u = 5 p --- (1)
6 u - 5 = 4 p
6 u = 4 p + 5 --- (2)

Make u the same.

(1) x 6
30 u = 30 p --- (3)

(2) x 5
30 u = 20 p + 25 --- (4)

(3) = (4)
30 p = 20 p + 25
30 p - 20 p = 25
10 p = 25
1 p = 25 ÷ 10 = 2.5

Volume of Tank R
= 4 p
= 4 x 2.5
= 10 ℓ

Answer(s): 10 ℓ