The figure shows a container made up of 3 sections. Cuboid P with a square base of side 9 cm and height 20 cm. Cube Q with a side of 13 cm. Cuboid R that is 66 cm by 10 cm by 41 cm. Water from a tap above flows down at a rate of 3.8 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 62 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of Q
= 13 x 13 x 13
= 2197 cm³ 

Volume of R
= 66 x 10 x 41
= 27060 cm³ 

1 ℓ = 1000 cm³ 
3.8 ℓ = 3800 cm³ 

Net increase in volume per minute
= 3800 - 1000
= 2800 cm³/min

Height of P to be filled with water
= 62 - (41 + 13)
= 8 cm

Volume of water in P
= 9 x 9 x 8
= 648 cm³ 

Volume of water in R, Q and part of P
= 27060 + 2197 + 648
= 29905 cm³ 

Time taken to reach height
= 29905 ÷ 2800
≈ 11 min (Correct to nearest whole number)

Answer(s): 11 min