4 pails and 3 containers can hold 21.3 litres of water.
1 pail and 1 container can hold 6.4 litres of water.

1. How many litres of water can 1 pail hold?
2. How many litres of water can 1 container hold?
3. How many litres of water can 7 containers hold?
4. How many litres of water can 9 containers and 4 pails?

(a)
4 pails + 3 containers = 21.3 --- (1)
1 pail + 1 container = 6.4 --- (2)

(2) x 3
1 pail + 1 container = 6.4
3 pails + 3 containers = 6.4 x 3
3 pails + 3 containers = 19.2 --- (3)

(1) - (3)
(4 pails + 3 containers) - (3 pails + 3 containers) = 21.3 - 19.2
4 pails + 3 containers - 3 pails - 3 containers = 2.1
4 pails - 3 pails + 3 containers - 3 containers = 2.1

1 pail = 2.1

Volume of 1 pail = 2.1 ℓ

(b)
Substitute 1 pail = 2.1 into (2).
1 pail + 1 container = 6.4
2.1 + 1 container = 6.4

1 container = 6.4 - 2.1 = 4.3

Volume of 1 container = 4.3 ℓ

(c)
Volume of 7 containers
= 7 x 4.3
= 30.1 ℓ

(d)
Volume of 9 containers and 4 pails
= 9 x 4.3 + 4 x 2.1
= 38.7 + 8.4
= 47.1 ℓ

Answer(s): (a) 2.1 ℓ; (b) 4.3 ℓ; (c) 30.1 ℓ; (d) 47.1 ℓ