The figure shows a tank made up of 3 sections. Cuboid E with a square base of side 4 cm and height 34 cm. Cube F with a side of 12 cm. Cuboid G that is 77 cm by 28 cm by 40 cm. Water from a tap above flows down at a rate of 2.5 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 58 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
= 77 x 28 x 40
= 86240 cm³ 

2 ℓ = 2000 cm³ 
2.5 ℓ = 2500 cm³ 

Net increase in volume per minute
= 2500 - 2000
= 500 cm³/min

Height of E to be filled with water
= 58 - (40 + 12)
= 6 cm

Volume of water in E
= 4 x 4 x 6
= 96 cm³ 

Volume of water in G, F and part of E
= 86240 + 1728 + 96
= 88064 cm³ 

Time taken to reach height
= 88064 ÷ 500
≈ 176 min (Correct to nearest whole number)

Answer(s): 176 min