The figure shows a container made up of 3 sections. Cuboid G with a square base of side 9 cm and height 49 cm. Cube H with a side of 14 cm. Cuboid J that is 63 cm by 19 cm by 41 cm. Water from a tap above flows down at a rate of 3.5 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 61 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of H
= 14 x 14 x 14
= 2744 cm³ 

Volume of J
= 63 x 19 x 41
= 49077 cm³ 

2 ℓ = 2000 cm³ 
3.5 ℓ = 3500 cm³ 

Net increase in volume per minute
= 3500 - 2000
= 1500 cm³/min

Height of G to be filled with water
= 61 - (41 + 14)
= 6 cm

Volume of water in G
= 9 x 9 x 6
= 486 cm³ 

Volume of water in J, H and part of G
= 49077 + 2744 + 486
= 52307 cm³ 

Time taken to reach height
= 52307 ÷ 1500
≈ 35 min (Correct to nearest whole number)

Answer(s): 35 min