The figure shows a container made up of 3 sections. Cuboid K with a square base of side 14 cm and height 35 cm. Cube L with a side of 11 cm. Cuboid M that is 75 cm by 15 cm by 45 cm. Water from a tap above flows down at a rate of 3.2 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 69 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of L
= 11 x 11 x 11
= 1331 cm³ 

Volume of M
= 75 x 15 x 45
= 50625 cm³ 

2 ℓ = 2000 cm³ 
3.2 ℓ = 3200 cm³ 

Net increase in volume per minute
= 3200 - 2000
= 1200 cm³/min

Height of K to be filled with water
= 69 - (45 + 11)
= 13 cm

Volume of water in K
= 14 x 14 x 13
= 2548 cm³ 

Volume of water in M, L and part of K
= 50625 + 1331 + 2548
= 54504 cm³ 

Time taken to reach height
= 54504 ÷ 1200
≈ 45 min (Correct to nearest whole number)

Answer(s): 45 min