The figure shows a container made up of 3 sections. Cuboid C with a square base of side 9 cm and height 45 cm. Cube D with a side of 17 cm. Cuboid E that is 76 cm by 13 cm by 41 cm. Water from a tap above flows down at a rate of 3.1 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 container to a height of 65 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of D
= 17 x 17 x 17
= 4913 cm³ 

Volume of E
= 76 x 13 x 41
= 40508 cm³ 

2 ℓ = 2000 cm³ 
3.1 ℓ = 3100 cm³ 

Net increase in volume per minute
= 3100 - 2000
= 1100 cm³/min

Height of C to be filled with water
= 65 - (41 + 17)
= 7 cm

Volume of water in C
= 9 x 9 x 7
= 567 cm³ 

Volume of water in E, D and part of C
= 40508 + 4913 + 567
= 45988 cm³ 

Time taken to reach height
= 45988 ÷ 1100
≈ 42 min (Correct to nearest whole number)

Answer(s): 42 min