The figure shows a tank made up of 3 sections. Cuboid D with a square base of side 25 cm and height 50 cm. Cube E with a side of 17 cm. Cuboid F that is 62 cm by 21 cm by 41 cm. Water from a tap above flows down at a rate of 3.8 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 tank to a height of 64 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of E
= 17 x 17 x 17
= 4913 cm³ 

Volume of F
= 62 x 21 x 41
= 53382 cm³ 

2 ℓ = 2000 cm³ 
3.8 ℓ = 3800 cm³ 

Net increase in volume per minute
= 3800 - 2000
= 1800 cm³/min

Height of D to be filled with water
= 64 - (41 + 17)
= 6 cm

Volume of water in D
= 25 x 25 x 6
= 3750 cm³ 

Volume of water in F, E and part of D
= 53382 + 4913 + 3750
= 62045 cm³ 

Time taken to reach height
= 62045 ÷ 1800
≈ 34 min (Correct to nearest whole number)

Answer(s): 34 min