The figure shows a tank made up of 3 sections. Cuboid H with a square base of side 9 cm and height 46 cm. Cube J with a side of 14 cm. Cuboid K that is 76 cm by 19 cm by 43 cm. Water from a tap above flows down at a rate of 3.2 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 63 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of J
= 14 x 14 x 14
= 2744 cm³ 

Volume of K
= 76 x 19 x 43
= 62092 cm³ 

2 ℓ = 2000 cm³ 
3.2 ℓ = 3200 cm³ 

Net increase in volume per minute
= 3200 - 2000
= 1200 cm³/min

Height of H to be filled with water
= 63 - (43 + 14)
= 6 cm

Volume of water in H
= 9 x 9 x 6
= 486 cm³ 

Volume of water in K, J and part of H
= 62092 + 2744 + 486
= 65322 cm³ 

Time taken to reach height
= 65322 ÷ 1200
≈ 54 min (Correct to nearest whole number)

Answer(s): 54 min