The figure shows a tank made up of 3 sections. Cuboid T with a square base of side 25 cm and height 47 cm. Cube U with a side of 12 cm. Cuboid V that is 61 cm by 16 cm by 44 cm. Water from a tap above flows down at a rate of 2.7 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 tank to a height of 67 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of U
= 12 x 12 x 12
= 1728 cm³ 

Volume of V
= 61 x 16 x 44
= 42944 cm³ 

1 ℓ = 1000 cm³ 
2.7 ℓ = 2700 cm³ 

Net increase in volume per minute
= 2700 - 1000
= 1700 cm³/min

Height of T to be filled with water
= 67 - (44 + 12)
= 11 cm

Volume of water in T
= 25 x 25 x 11
= 6875 cm³ 

Volume of water in V, U and part of T
= 42944 + 1728 + 6875
= 51547 cm³ 

Time taken to reach height
= 51547 ÷ 1700
≈ 30 min (Correct to nearest whole number)

Answer(s): 30 min