The figure shows a container made up of 3 sections. Cuboid J with a square base of side 14 cm and height 34 cm. Cube K with a side of 12 cm. Cuboid L that is 62 cm by 13 cm by 49 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 67 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of K
= 12 x 12 x 12
= 1728 cm³ 

Volume of L
= 62 x 13 x 49
= 39494 cm³ 

1 ℓ = 1000 cm³ 
3.1 ℓ = 3100 cm³ 

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

Height of J to be filled with water
= 67 - (49 + 12)
= 6 cm

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

Volume of water in L, K and part of J
= 39494 + 1728 + 1176
= 42398 cm³ 

Time taken to reach height
= 42398 ÷ 2100
≈ 20 min (Correct to nearest whole number)

Answer(s): 20 min