The figure shows a container made up of 3 sections. Cuboid P with a square base of side 14 cm and height 42 cm. Cube Q with a side of 10 cm. Cuboid R that is 65 cm by 11 cm by 46 cm. Water from a tap above flows down at a rate of 3.7 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 70 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of Q
= 10 x 10 x 10
= 1000 cm³ 

Volume of R
= 65 x 11 x 46
= 32890 cm³ 

1 ℓ = 1000 cm³ 
3.7 ℓ = 3700 cm³ 

Net increase in volume per minute
= 3700 - 1000
= 2700 cm³/min

Height of P to be filled with water
= 70 - (46 + 10)
= 14 cm

Volume of water in P
= 14 x 14 x 14
= 2744 cm³ 

Volume of water in R, Q and part of P
= 32890 + 1000 + 2744
= 36634 cm³ 

Time taken to reach height
= 36634 ÷ 2700
≈ 14 min (Correct to nearest whole number)

Answer(s): 14 min