The figure shows a tank made up of 3 sections. Cuboid Z with a square base of side 9 cm and height 40 cm. Cube A with a side of 13 cm. Cuboid B that is 74 cm by 10 cm by 42 cm. Water from a tap above flows down at a rate of 2.2 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 tank to a height of 62 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of A
= 13 x 13 x 13
= 2197 cm³ 

Volume of B
= 74 x 10 x 42
= 31080 cm³ 

1 ℓ = 1000 cm³ 
2.2 ℓ = 2200 cm³ 

Net increase in volume per minute
= 2200 - 1000
= 1200 cm³/min

Height of Z to be filled with water
= 62 - (42 + 13)
= 7 cm

Volume of water in Z
= 9 x 9 x 7
= 567 cm³ 

Volume of water in B, A and part of Z
= 31080 + 2197 + 567
= 33844 cm³ 

Time taken to reach height
= 33844 ÷ 1200
≈ 28 min (Correct to nearest whole number)

Answer(s): 28 min