The figure shows a container made up of 3 sections. Cuboid A with a square base of side 9 cm and height 44 cm. Cube B with a side of 12 cm. Cuboid C that is 75 cm by 27 cm by 47 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 1 litre per minute. How long did it take to fill up the container to a height of 70 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of B
= 12 x 12 x 12
= 1728 cm³ 

Volume of C
= 75 x 27 x 47
= 95175 cm³ 

1 ℓ = 1000 cm³ 
3.6 ℓ = 3600 cm³ 

Net increase in volume per minute
= 3600 - 1000
= 2600 cm³/min

Height of A to be filled with water
= 70 - (47 + 12)
= 11 cm

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

Volume of water in C, B and part of A
= 95175 + 1728 + 891
= 97794 cm³ 

Time taken to reach height
= 97794 ÷ 2600
≈ 38 min (Correct to nearest whole number)

Answer(s): 38 min