The figure shows a tank made up of 3 sections. Cuboid E with a square base of side 14 cm and height 40 cm. Cube F with a side of 12 cm. Cuboid G that is 64 cm by 30 cm by 41 cm. Water from a tap above flows down at a rate of 3.9 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 F
= 12 x 12 x 12
= 1728 cm³ 

Volume of G
= 64 x 30 x 41
= 78720 cm³ 

2 ℓ = 2000 cm³ 
3.9 ℓ = 3900 cm³ 

Net increase in volume per minute
= 3900 - 2000
= 1900 cm³/min

Height of E to be filled with water
= 66 - (41 + 12)
= 13 cm

Volume of water in E
= 14 x 14 x 13
= 2548 cm³ 

Volume of water in G, F and part of E
= 78720 + 1728 + 2548
= 82996 cm³ 

Time taken to reach height
= 82996 ÷ 1900
≈ 44 min (Correct to nearest whole number)

Answer(s): 44 min