The figure shows a container made up of 3 sections. Cuboid V with a square base of side 14 cm and height 30 cm. Cube W with a side of 19 cm. Cuboid X that is 70 cm by 24 cm by 41 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 67 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of W
= 19 x 19 x 19
= 6859 cm³ 

Volume of X
= 70 x 24 x 41
= 68880 cm³ 

1 ℓ = 1000 cm³ 
2.5 ℓ = 2500 cm³ 

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

Height of V to be filled with water
= 67 - (41 + 19)
= 7 cm

Volume of water in V
= 14 x 14 x 7
= 1372 cm³ 

Volume of water in X, W and part of V
= 68880 + 6859 + 1372
= 77111 cm³ 

Time taken to reach height
= 77111 ÷ 1500
≈ 51 min (Correct to nearest whole number)

Answer(s): 51 min