A rectangular tank measuring 140 cm by 40 cm by 120 cm is 50% filled with water. 7 identical containers of water that are completely filled are then scooped out from it. The water level drops to 40 cm. The remaining amount of water in the tank is later poured into a container that contains 40 litres of water. The water is then drained out through a tap found at the bottom of the container at 20 litres per minute.

1. What is the capacity of each pail? Answer in litres.
2. How long did it take to drain the water from the container completely? Answer in terms of min.

(a)
Original height of water in the tank 
= 120 x 50%
= 60 cm

Difference in height when 7 containers were scooped out
= 60 - 40
= 20 cm

Volume of 7 containers
= 140 x 40 x 20
= 112000 cm³ 

Volume of 1 container 
= 112000 ÷ 7
= 16000 mℓ
= 16 ℓ

(b)
Remaining water in the tank 
= 140 x 40 x 40
= 224000 cm³

40 ℓ = 40000 mℓ

Total volume of water to drain
= 224000 + 40000
= 264000 mℓ

20 ℓ = 20000 mℓ

Time taken to drain the water
= 264000 ÷ 20000
= 13.2 min

Answer(s): (a) 16 ℓ; (b) 13.2 min