The figure shows a container made up of 3 sections. Cuboid X with a square base of side 4 cm and height 24 cm. Cube Y with a side of 11 cm. Cuboid Z that is 67 cm by 12 cm by 43 cm. Water from a tap above flows down at a rate of 3.1 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 64 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of Y
= 11 x 11 x 11
= 1331 cm³ 

Volume of Z
= 67 x 12 x 43
= 34572 cm³ 

1 ℓ = 1000 cm³ 
3.1 ℓ = 3100 cm³ 

Net increase in volume per minute
= 3100 - 1000
= 2100 cm³/min

Height of X to be filled with water
= 64 - (43 + 11)
= 10 cm

Volume of water in X
= 4 x 4 x 10
= 160 cm³ 

Volume of water in Z, Y and part of X
= 34572 + 1331 + 160
= 36063 cm³ 

Time taken to reach height
= 36063 ÷ 2100
≈ 17 min (Correct to nearest whole number)

Answer(s): 17 min