Michael and Justin each had the same volume of water. The water was used to pour into identical bottles. Michael filled up 12 bottles and had 9.9 ℓ of water left. Justin filled up 8 bottles and had 11.1 ℓ of water left.

1. What was the capacity of each bottle? Give your answer in millilitres.
2. What was the total volume of water Michael and Justin had at first? Give your answer in litres.

(a)
Difference between the number of bottles
= 12 - 8
= 4

Difference between the volume of water left
= 11.1 - 9.9
= 1.2 ℓ

Volume of 4 bottles = 1.2 ℓ

Volume of 1 bottle
= 1.2 ÷ 4
= 0.3 ℓ

1 ℓ = 1000 mℓ
0.3 ℓ = 0.3 x 1000 = 300 mℓ

(b)
Volume of 8 bottles 
= 8 x 0.3
= 2.4 ℓ

Volume of water that Justin had at first
= 2.4 + 11.1
= 13.5 ℓ

Total volume of water that Michael and Justin had at first
= 2 x 13.5
= 27 ℓ

Answer(s): (a) 300 mℓ (b) 27 ℓ