5 tanks and 4 pails can hold 46.8 litres of water.
1 tank and 1 pail can hold 9.9 litres of water.

1. How many litres of water can 1 tank hold?
2. How many litres of water can 1 pail hold?
3. How many litres of water can 9 pails hold?
4. How many litres of water can 6 pails and 5 tanks?

(a)
5 tanks + 4 pails = 46.8 --- (1)
1 tank + 1 pail = 9.9 --- (2)

(2) x 4
1 tank + 1 pail = 9.9
4 tanks + 4 pails = 9.9 x 4
4 tanks + 4 pails = 39.6 --- (3)

(1) - (3)
(5 tanks + 4 pails) - (4 tanks + 4 pails) = 46.8 - 39.6
5 tanks + 4 pails - 4 tanks - 4 pails = 7.2
5 tanks - 4 tanks + 4 pails - 4 pails = 7.2

1 tank = 7.2

Volume of 1 tank = 7.2 ℓ

(b)
Substitute 1 tank = 7.2 into (2).
1 tank + 1 pail = 9.9
7.2 + 1 pail = 9.9

1 pail = 9.9 - 7.2 = 2.7

Volume of 1 pail = 2.7 ℓ

(c)
Volume of 9 pails
= 9 x 2.7
= 24.3 ℓ

(d)
Volume of 6 pails and 5 tanks
= 6 x 2.7 + 5 x 7.2
= 16.2 + 36
= 52.2 ℓ

Answer(s): (a) 7.2 ℓ; (b) 2.7 ℓ; (c) 24.3 ℓ; (d) 52.2 ℓ