The figure shows a container made up of 3 sections. Cuboid D with a square base of side 9 cm and height 45 cm. Cube E with a side of 10 cm. Cuboid F that is 63 cm by 30 cm by 42 cm. Water from a tap above flows down at a rate of 3.2 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 E
= 10 x 10 x 10
= 1000 cm³ 

Volume of F
= 63 x 30 x 42
= 79380 cm³ 

2 ℓ = 2000 cm³ 
3.2 ℓ = 3200 cm³ 

Net increase in volume per minute
= 3200 - 2000
= 1200 cm³/min

Height of D to be filled with water
= 65 - (42 + 10)
= 13 cm

Volume of water in D
= 9 x 9 x 13
= 1053 cm³ 

Volume of water in F, E and part of D
= 79380 + 1000 + 1053
= 81433 cm³ 

Time taken to reach height
= 81433 ÷ 1200
≈ 68 min (Correct to nearest whole number)

Answer(s): 68 min