The figure shows a tank made up of 3 sections. Cuboid E with a square base of side 9 cm and height 23 cm. Cube F with a side of 10 cm. Cuboid G that is 67 cm by 13 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 64 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of F
= 10 x 10 x 10
= 1000 cm³ 

Volume of G
= 67 x 13 x 43
= 37453 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
= 64 - (43 + 10)
= 11 cm

Volume of water in E
= 9 x 9 x 11
= 891 cm³ 

Volume of water in G, F and part of E
= 37453 + 1000 + 891
= 39344 cm³ 

Time taken to reach height
= 39344 ÷ 1600
≈ 25 min (Correct to nearest whole number)

Answer(s): 25 min