The figure shows a tank made up of 3 sections. Cuboid E with a square base of side 25 cm and height 33 cm. Cube F with a side of 11 cm. Cuboid G that is 74 cm by 15 cm by 43 cm. Water from a tap above flows down at a rate of 3.6 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 60 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of F
= 11 x 11 x 11
= 1331 cm³ 

Volume of G
= 74 x 15 x 43
= 47730 cm³ 

2 ℓ = 2000 cm³ 
3.6 ℓ = 3600 cm³ 

Net increase in volume per minute
= 3600 - 2000
= 1600 cm³/min

Height of E to be filled with water
= 60 - (43 + 11)
= 6 cm

Volume of water in E
= 25 x 25 x 6
= 3750 cm³ 

Volume of water in G, F and part of E
= 47730 + 1331 + 3750
= 52811 cm³ 

Time taken to reach height
= 52811 ÷ 1600
≈ 33 min (Correct to nearest whole number)

Answer(s): 33 min