Isaiah has 2 tanks. Tank Q and Tank R are of different capacities. If Tank Q is filled by a tap at a rate of 3 litres per minute and Tank R is filled by a tap at a rate of 5 litres per minute, when Tank Q is completely filled, 8 litres of water flowed out from Tank R. If Tank Q is filled by a tap at a rate of 4 litres per minute and Tank R is filled by a tap at a rate of 3 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	3 u	5 u - 8	4 p	3 p x 2 = 6 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 = 6 p
5 u = 6 p + 8 --- (2)

Make u the same.

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

(2) x 3
15 u = 18 p + 24 --- (4)

(3) = (4)
20 p = 18 p + 24
20 p - 18 p = 24
2 p = 24
1 p = 24 ÷ 2 = 12

Volume of Tank R
= 6 p
= 6 x 12
= 72 ℓ

Answer(s): 72 ℓ