The figure shows a tank made up of 3 sections. Cuboid F with a square base of side 14 cm and height 34 cm. Cube G with a side of 15 cm. Cuboid H that is 67 cm by 11 cm by 44 cm. Water from a tap above flows down at a rate of 2.3 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 70 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of G
= 15 x 15 x 15
= 3375 cm³ 

Volume of H
= 67 x 11 x 44
= 32428 cm³ 

1 ℓ = 1000 cm³ 
2.3 ℓ = 2300 cm³ 

Net increase in volume per minute
= 2300 - 1000
= 1300 cm³/min

Height of F to be filled with water
= 70 - (44 + 15)
= 11 cm

Volume of water in F
= 14 x 14 x 11
= 2156 cm³ 

Volume of water in H, G and part of F
= 32428 + 3375 + 2156
= 37959 cm³ 

Time taken to reach height
= 37959 ÷ 1300
≈ 29 min (Correct to nearest whole number)

Answer(s): 29 min