The figure shows a container made up of 3 sections. Cuboid V with a square base of side 9 cm and height 38 cm. Cube W with a side of 12 cm. Cuboid X that is 71 cm by 27 cm by 40 cm. Water from a tap above flows down at a rate of 3.4 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 69 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of W
= 12 x 12 x 12
= 1728 cm³ 

Volume of X
= 71 x 27 x 40
= 76680 cm³ 

1 ℓ = 1000 cm³ 
3.4 ℓ = 3400 cm³ 

Net increase in volume per minute
= 3400 - 1000
= 2400 cm³/min

Height of V to be filled with water
= 69 - (40 + 12)
= 17 cm

Volume of water in V
= 9 x 9 x 17
= 1377 cm³ 

Volume of water in X, W and part of V
= 76680 + 1728 + 1377
= 79785 cm³ 

Time taken to reach height
= 79785 ÷ 2400
≈ 33 min (Correct to nearest whole number)

Answer(s): 33 min