The figure shows a container made up of 3 sections. Cuboid G with a square base of side 4 cm and height 29 cm. Cube H with a side of 19 cm. Cuboid J that is 71 cm by 26 cm by 40 cm. Water from a tap above flows down at a rate of 2.9 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 66 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of H
= 19 x 19 x 19
= 6859 cm³ 

Volume of J
= 71 x 26 x 40
= 73840 cm³ 

2 ℓ = 2000 cm³ 
2.9 ℓ = 2900 cm³ 

Net increase in volume per minute
= 2900 - 2000
= 900 cm³/min

Height of G to be filled with water
= 66 - (40 + 19)
= 7 cm

Volume of water in G
= 4 x 4 x 7
= 112 cm³ 

Volume of water in J, H and part of G
= 73840 + 6859 + 112
= 80811 cm³ 

Time taken to reach height
= 80811 ÷ 900
≈ 90 min (Correct to nearest whole number)

Answer(s): 90 min