The figure shows a tank made up of 3 sections. Cuboid H with a square base of side 25 cm and height 46 cm. Cube J with a side of 14 cm. Cuboid K that is 78 cm by 20 cm by 47 cm. Water from a tap above flows down at a rate of 2.4 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 70 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
= 78 x 20 x 47
= 73320 cm³ 

2 ℓ = 2000 cm³ 
2.4 ℓ = 2400 cm³ 

Net increase in volume per minute
= 2400 - 2000
= 400 cm³/min

Height of H to be filled with water
= 70 - (47 + 14)
= 9 cm

Volume of water in H
= 25 x 25 x 9
= 5625 cm³ 

Volume of water in K, J and part of H
= 73320 + 2744 + 5625
= 81689 cm³ 

Time taken to reach height
= 81689 ÷ 400
≈ 204 min (Correct to nearest whole number)

Answer(s): 204 min