John has 2 containers. Container Q and Container R are of different capacities. If Container Q is filled by a tap at a rate of 5 litres per minute and Container R is filled by a tap at a rate of 7 litres per minute, when Container Q is completely filled, 8 litres of water flowed out from Container R. If Container Q is filled by a tap at a rate of 6 litres per minute and Container R is filled by a tap at a rate of 4 litres per minute, when Container Q is completely filled, Container R is only half-filled. What is the capacity of Container R? Express your answer in litres.

	Scenario 1		Scenario 2
Container type	Container Q	Container R	Container Q	Container R
Volume of the container	5 u	7 u - 8	6 p	4 p x 2 = 8 p

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

5 u = 6 p --- (1)
7 u - 8 = 8 p
7 u = 8 p + 8 --- (2)

Make u the same.

(1) x 7
35 u = 42 p --- (3)

(2) x 5
35 u = 40 p + 40 --- (4)

(3) = (4)
42 p = 40 p + 40
42 p - 40 p = 40
2 p = 40
1 p = 40 ÷ 2 = 20

Volume of Container R
= 8 p
= 8 x 20
= 160 ℓ

Answer(s): 160 ℓ