The figure shows a container made up of 3 sections. Cuboid K with a square base of side 14 cm and height 30 cm. Cube L with a side of 11 cm. Cuboid M that is 71 cm by 21 cm by 47 cm. Water from a tap above flows down at a rate of 2.5 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 66 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
= 71 x 21 x 47
= 70077 cm³ 

1 ℓ = 1000 cm³ 
2.5 ℓ = 2500 cm³ 

Net increase in volume per minute
= 2500 - 1000
= 1500 cm³/min

Height of K to be filled with water
= 66 - (47 + 11)
= 8 cm

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

Volume of water in M, L and part of K
= 70077 + 1331 + 1568
= 72976 cm³ 

Time taken to reach height
= 72976 ÷ 1500
≈ 49 min (Correct to nearest whole number)

Answer(s): 49 min