The figure shows a container made up of 3 sections. Cuboid K with a square base of side 14 cm and height 46 cm. Cube L with a side of 17 cm. Cuboid M that is 65 cm by 16 cm by 43 cm. Water from a tap above flows down at a rate of 2.8 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 L
= 17 x 17 x 17
= 4913 cm³ 

Volume of M
= 65 x 16 x 43
= 44720 cm³ 

2 ℓ = 2000 cm³ 
2.8 ℓ = 2800 cm³ 

Net increase in volume per minute
= 2800 - 2000
= 800 cm³/min

Height of K to be filled with water
= 68 - (43 + 17)
= 8 cm

Volume of water in K
= 14 x 14 x 8
= 1568 cm³ 

Volume of water in M, L and part of K
= 44720 + 4913 + 1568
= 51201 cm³ 

Time taken to reach height
= 51201 ÷ 800
≈ 64 min (Correct to nearest whole number)

Answer(s): 64 min