The figure shows a tank made up of 3 sections. Cuboid V with a square base of side 25 cm and height 32 cm. Cube W with a side of 10 cm. Cuboid X that is 80 cm by 26 cm by 42 cm. Water from a tap above flows down at a rate of 3.7 litres per minute while water is drained out from the bottom at a rate of 2 litre per minute. How long did it take to fill up the tank to a height of 66 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of W
= 10 x 10 x 10
= 1000 cm³ 

Volume of X
= 80 x 26 x 42
= 87360 cm³ 

2 ℓ = 2000 cm³ 
3.7 ℓ = 3700 cm³ 

Net increase in volume per minute
= 3700 - 2000
= 1700 cm³/min

Height of V to be filled with water
= 66 - (42 + 10)
= 14 cm

Volume of water in V
= 25 x 25 x 14
= 8750 cm³ 

Volume of water in X, W and part of V
= 87360 + 1000 + 8750
= 97110 cm³ 

Time taken to reach height
= 97110 ÷ 1700
≈ 57 min (Correct to nearest whole number)

Answer(s): 57 min