Kaylee has 2 tanks. Tank L and Tank M are of different capacities. If Tank L is filled by a tap at a rate of 4 litres per minute and Tank M is filled by a tap at a rate of 7 litres per minute, when Tank L is completely filled, 6 litres of water flowed out from Tank M. If Tank L is filled by a tap at a rate of 6 litres per minute and Tank M is filled by a tap at a rate of 4 litres per minute, when Tank L is completely filled, Tank M is only half-filled. What is the capacity of Tank M? Express your answer in litres.

	Scenario 1		Scenario 2
Tank type	Tank L	Tank M	Tank L	Tank M
Volume of the tank	4 u	7 u - 6	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.

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

Make u the same.

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

(2) x 4
28 u = 32 p + 24 --- (4)

(3) = (4)
42 p = 32 p + 24
42 p - 32 p = 24
10 p = 24
1 p = 24 ÷ 10 = 2.4

Volume of Tank M
= 8 p
= 8 x 2.4
= 19.2 ℓ

Answer(s): 19.2 ℓ