The figure shows a container made up of 3 sections. Cuboid X with a square base of side 9 cm and height 29 cm. Cube Y with a side of 15 cm. Cuboid Z that is 63 cm by 11 cm by 44 cm. Water from a tap above flows down at a rate of 2.8 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 Y
= 15 x 15 x 15
= 3375 cm³ 

Volume of Z
= 63 x 11 x 44
= 30492 cm³ 

1 ℓ = 1000 cm³ 
2.8 ℓ = 2800 cm³ 

Net increase in volume per minute
= 2800 - 1000
= 1800 cm³/min

Height of X to be filled with water
= 69 - (44 + 15)
= 10 cm

Volume of water in X
= 9 x 9 x 10
= 810 cm³ 

Volume of water in Z, Y and part of X
= 30492 + 3375 + 810
= 34677 cm³ 

Time taken to reach height
= 34677 ÷ 1800
≈ 19 min (Correct to nearest whole number)

Answer(s): 19 min