The figure shows a container made up of 3 sections. Cuboid F with a square base of side 4 cm and height 30 cm. Cube G with a side of 12 cm. Cuboid H that is 78 cm by 28 cm by 48 cm. Water from a tap above flows down at a rate of 2.8 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 69 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of G
= 12 x 12 x 12
= 1728 cm³ 

Volume of H
= 78 x 28 x 48
= 104832 cm³ 

1 ℓ = 1000 cm³ 
2.8 ℓ = 2800 cm³ 

Net increase in volume per minute
= 2800 - 1000
= 1800 cm³/min

Height of F to be filled with water
= 69 - (48 + 12)
= 9 cm

Volume of water in F
= 4 x 4 x 9
= 144 cm³ 

Volume of water in H, G and part of F
= 104832 + 1728 + 144
= 106704 cm³ 

Time taken to reach height
= 106704 ÷ 1800
≈ 59 min (Correct to nearest whole number)

Answer(s): 59 min