The figure shows a tank made up of 3 sections. Cuboid R with a square base of side 4 cm and height 44 cm. Cube S with a side of 11 cm. Cuboid T that is 63 cm by 20 cm by 44 cm. Water from a tap above flows down at a rate of 3.7 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 66 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of S
= 11 x 11 x 11
= 1331 cm³ 

Volume of T
= 63 x 20 x 44
= 55440 cm³ 

2 ℓ = 2000 cm³ 
3.7 ℓ = 3700 cm³ 

Net increase in volume per minute
= 3700 - 2000
= 1700 cm³/min

Height of R to be filled with water
= 66 - (44 + 11)
= 11 cm

Volume of water in R
= 4 x 4 x 11
= 176 cm³ 

Volume of water in T, S and part of R
= 55440 + 1331 + 176
= 56947 cm³ 

Time taken to reach height
= 56947 ÷ 1700
≈ 33 min (Correct to nearest whole number)

Answer(s): 33 min