The figure shows a container made up of 3 sections. Cuboid Q with a square base of side 14 cm and height 38 cm. Cube R with a side of 11 cm. Cuboid S that is 78 cm by 29 cm by 50 cm. Water from a tap above flows down at a rate of 2.2 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 67 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of R
= 11 x 11 x 11
= 1331 cm³ 

Volume of S
= 78 x 29 x 50
= 113100 cm³ 

1 ℓ = 1000 cm³ 
2.2 ℓ = 2200 cm³ 

Net increase in volume per minute
= 2200 - 1000
= 1200 cm³/min

Height of Q to be filled with water
= 67 - (50 + 11)
= 6 cm

Volume of water in Q
= 14 x 14 x 6
= 1176 cm³ 

Volume of water in S, R and part of Q
= 113100 + 1331 + 1176
= 115607 cm³ 

Time taken to reach height
= 115607 ÷ 1200
≈ 96 min (Correct to nearest whole number)

Answer(s): 96 min