Jayden has 2 containers. Container N and Container P are of different capacities. If Container N is filled by a tap at a rate of 3 litres per minute and Container P is filled by a tap at a rate of 7 litres per minute, when Container N is completely filled, 7 litres of water flowed out from Container P. If Container N is filled by a tap at a rate of 6 litres per minute and Container P is filled by a tap at a rate of 3 litres per minute, when Container N is completely filled, Container P is only one-third-filled. What is the capacity of Container P? Express your answer in litres.

	Scenario 1		Scenario 2
Container type	Container N	Container P	Container N	Container P
Volume of the container	3 u	7 u - 7	6 p	3 p x 3 = 9 p

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

3 u = 6 p --- (1)
7 u - 7 = 9 p
7 u = 9 p + 7 --- (2)

Make u the same.

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

(2) x 3
21 u = 27 p + 21 --- (4)

(3) = (4)
42 p = 27 p + 21
42 p - 27 p = 21
15 p = 21
1 p = 21 ÷ 15 = 1.4

Volume of Container P
= 9 p
= 9 x 1.4
= 12.6 ℓ

Answer(s): 12.6 ℓ