The figure shows a container made up of 3 sections. Cuboid V with a square base of side 4 cm and height 24 cm. Cube W with a side of 13 cm. Cuboid X that is 72 cm by 13 cm by 44 cm. Water from a tap above flows down at a rate of 2.9 litres per minute while water is drained out from the bottom at a rate of 1 litre per minute. How long did it take to fill up the container to a height of 63 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of W
= 13 x 13 x 13
= 2197 cm³ 

Volume of X
= 72 x 13 x 44
= 41184 cm³ 

1 ℓ = 1000 cm³ 
2.9 ℓ = 2900 cm³ 

Net increase in volume per minute
= 2900 - 1000
= 1900 cm³/min

Height of V to be filled with water
= 63 - (44 + 13)
= 6 cm

Volume of water in V
= 4 x 4 x 6
= 96 cm³ 

Volume of water in X, W and part of V
= 41184 + 2197 + 96
= 43477 cm³ 

Time taken to reach height
= 43477 ÷ 1900
≈ 23 min (Correct to nearest whole number)

Answer(s): 23 min