The figure shows a container made up of 3 sections. Cuboid J with a square base of side 4 cm and height 23 cm. Cube K with a side of 12 cm. Cuboid L that is 74 cm by 15 cm by 50 cm. Water from a tap above flows down at a rate of 3.3 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 K
= 12 x 12 x 12
= 1728 cm³ 

Volume of L
= 74 x 15 x 50
= 55500 cm³ 

2 ℓ = 2000 cm³ 
3.3 ℓ = 3300 cm³ 

Net increase in volume per minute
= 3300 - 2000
= 1300 cm³/min

Height of J to be filled with water
= 68 - (50 + 12)
= 6 cm

Volume of water in J
= 4 x 4 x 6
= 96 cm³ 

Volume of water in L, K and part of J
= 55500 + 1728 + 96
= 57324 cm³ 

Time taken to reach height
= 57324 ÷ 1300
≈ 44 min (Correct to nearest whole number)

Answer(s): 44 min