The figure shows a container made up of 3 sections. Cuboid Z with a square base of side 14 cm and height 42 cm. Cube A with a side of 15 cm. Cuboid B that is 79 cm by 11 cm by 41 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 62 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of A
= 15 x 15 x 15
= 3375 cm³ 

Volume of B
= 79 x 11 x 41
= 35629 cm³ 

1 ℓ = 1000 cm³ 
2.9 ℓ = 2900 cm³ 

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

Height of Z to be filled with water
= 62 - (41 + 15)
= 6 cm

Volume of water in Z
= 14 x 14 x 6
= 1176 cm³ 

Volume of water in B, A and part of Z
= 35629 + 3375 + 1176
= 40180 cm³ 

Time taken to reach height
= 40180 ÷ 1900
≈ 21 min (Correct to nearest whole number)

Answer(s): 21 min