The figure shows a container made up of 3 sections. Cuboid P with a square base of side 9 cm and height 26 cm. Cube Q with a side of 14 cm. Cuboid R that is 80 cm by 17 cm by 45 cm. Water from a tap above flows down at a rate of 2.4 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 68 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of Q
= 14 x 14 x 14
= 2744 cm³ 

Volume of R
= 80 x 17 x 45
= 61200 cm³ 

2 ℓ = 2000 cm³ 
2.4 ℓ = 2400 cm³ 

Net increase in volume per minute
= 2400 - 2000
= 400 cm³/min

Height of P to be filled with water
= 68 - (45 + 14)
= 9 cm

Volume of water in P
= 9 x 9 x 9
= 729 cm³ 

Volume of water in R, Q and part of P
= 61200 + 2744 + 729
= 64673 cm³ 

Time taken to reach height
= 64673 ÷ 400
≈ 162 min (Correct to nearest whole number)

Answer(s): 162 min