The figure shows a tank made up of 3 sections. Cuboid W with a square base of side 14 cm and height 28 cm. Cube X with a side of 10 cm. Cuboid Y that is 71 cm by 24 cm by 46 cm. Water from a tap above flows down at a rate of 2.7 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 64 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of X
= 10 x 10 x 10
= 1000 cm³ 

Volume of Y
= 71 x 24 x 46
= 78384 cm³ 

1 ℓ = 1000 cm³ 
2.7 ℓ = 2700 cm³ 

Net increase in volume per minute
= 2700 - 1000
= 1700 cm³/min

Height of W to be filled with water
= 64 - (46 + 10)
= 8 cm

Volume of water in W
= 14 x 14 x 8
= 1568 cm³ 

Volume of water in Y, X and part of W
= 78384 + 1000 + 1568
= 80952 cm³ 

Time taken to reach height
= 80952 ÷ 1700
≈ 48 min (Correct to nearest whole number)

Answer(s): 48 min