The figure shows a container made up of 3 sections. Cuboid N with a square base of side 14 cm and height 48 cm. Cube P with a side of 10 cm. Cuboid Q that is 76 cm by 10 cm by 42 cm. Water from a tap above flows down at a rate of 3.1 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 58 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of P
= 10 x 10 x 10
= 1000 cm³ 

Volume of Q
= 76 x 10 x 42
= 31920 cm³ 

1 ℓ = 1000 cm³ 
3.1 ℓ = 3100 cm³ 

Net increase in volume per minute
= 3100 - 1000
= 2100 cm³/min

Height of N to be filled with water
= 58 - (42 + 10)
= 6 cm

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

Volume of water in Q, P and part of N
= 31920 + 1000 + 1176
= 34096 cm³ 

Time taken to reach height
= 34096 ÷ 2100
≈ 16 min (Correct to nearest whole number)

Answer(s): 16 min