Victoria has 2 tanks. Tank J and Tank K are of different capacities. If Tank J is filled by a tap at a rate of 3 litres per minute and Tank K is filled by a tap at a rate of 5 litres per minute, when Tank J is completely filled, 7 litres of water flowed out from Tank K. If Tank J is filled by a tap at a rate of 4 litres per minute and Tank K is filled by a tap at a rate of 2 litres per minute, when Tank J is completely filled, Tank K is only one-third-filled. What is the capacity of Tank K? Express your answer in litres.

	Scenario 1		Scenario 2
Tank type	Tank J	Tank K	Tank J	Tank K
Volume of the tank	3 u	5 u - 7	4 p	2 p x 3 = 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 - 7 = 6 p
5 u = 6 p + 7 --- (2)

Make u the same.

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

(2) x 3
15 u = 18 p + 21 --- (4)

(3) = (4)
20 p = 18 p + 21
20 p - 18 p = 21
2 p = 21
1 p = 21 ÷ 2 = 10.5

Volume of Tank K
= 6 p
= 6 x 10.5
= 63 ℓ

Answer(s): 63 ℓ