The figure shows a container made up of 3 sections. Cuboid J with a square base of side 9 cm and height 41 cm. Cube K with a side of 12 cm. Cuboid L that is 66 cm by 25 cm by 40 cm. Water from a tap above flows down at a rate of 3.6 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 64 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
= 66 x 25 x 40
= 66000 cm³ 

1 ℓ = 1000 cm³ 
3.6 ℓ = 3600 cm³ 

Net increase in volume per minute
= 3600 - 1000
= 2600 cm³/min

Height of J to be filled with water
= 64 - (40 + 12)
= 12 cm

Volume of water in J
= 9 x 9 x 12
= 972 cm³ 

Volume of water in L, K and part of J
= 66000 + 1728 + 972
= 68700 cm³ 

Time taken to reach height
= 68700 ÷ 2600
≈ 26 min (Correct to nearest whole number)

Answer(s): 26 min