The figure shows a tank made up of 3 sections. Cuboid T with a square base of side 14 cm and height 34 cm. Cube U with a side of 17 cm. Cuboid V that is 78 cm by 23 cm by 40 cm. Water from a tap above flows down at a rate of 3.3 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 65 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of U
= 17 x 17 x 17
= 4913 cm³ 

Volume of V
= 78 x 23 x 40
= 71760 cm³ 

1 ℓ = 1000 cm³ 
3.3 ℓ = 3300 cm³ 

Net increase in volume per minute
= 3300 - 1000
= 2300 cm³/min

Height of T to be filled with water
= 65 - (40 + 17)
= 8 cm

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

Volume of water in V, U and part of T
= 71760 + 4913 + 1568
= 78241 cm³ 

Time taken to reach height
= 78241 ÷ 2300
≈ 34 min (Correct to nearest whole number)

Answer(s): 34 min