The figure shows a tank made up of 3 sections. Cuboid A with a square base of side 14 cm and height 24 cm. Cube B with a side of 10 cm. Cuboid C that is 65 cm by 23 cm by 45 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 1 litre per minute. How long did it take to fill up the tank to a height of 69 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of B
= 10 x 10 x 10
= 1000 cm³ 

Volume of C
= 65 x 23 x 45
= 67275 cm³ 

1 ℓ = 1000 cm³ 
3.2 ℓ = 3200 cm³ 

Net increase in volume per minute
= 3200 - 1000
= 2200 cm³/min

Height of A to be filled with water
= 69 - (45 + 10)
= 14 cm

Volume of water in A
= 14 x 14 x 14
= 2744 cm³ 

Volume of water in C, B and part of A
= 67275 + 1000 + 2744
= 71019 cm³ 

Time taken to reach height
= 71019 ÷ 2200
≈ 32 min (Correct to nearest whole number)

Answer(s): 32 min