6 pails and 5 tanks can hold 47.4 litres of water.
1 pail and 1 tank can hold 8.7 litres of water.

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

(a)
6 pails + 5 tanks = 47.4 --- (1)
1 pail + 1 tank = 8.7 --- (2)

(2) x 5
1 pail + 1 tank = 8.7
5 pails + 5 tanks = 8.7 x 5
5 pails + 5 tanks = 43.5 --- (3)

(1) - (3)
(6 pails + 5 tanks) - (5 pails + 5 tanks) = 47.4 - 43.5
6 pails + 5 tanks - 5 pails - 5 tanks = 3.9
6 pails - 5 pails + 5 tanks - 5 tanks = 3.9

1 pail = 3.9

Volume of 1 pail = 3.9 ℓ

(b)
Substitute 1 pail = 3.9 into (2).
1 pail + 1 tank = 8.7
3.9 + 1 tank = 8.7

1 tank = 8.7 - 3.9 = 4.8

Volume of 1 tank = 4.8 ℓ

(c)
Volume of 4 tanks
= 4 x 4.8
= 19.2 ℓ

(d)
Volume of 5 tanks and 6 pails
= 5 x 4.8 + 6 x 3.9
= 24 + 23.4
= 47.4 ℓ

Answer(s): (a) 3.9 ℓ; (b) 4.8 ℓ; (c) 19.2 ℓ; (d) 47.4 ℓ