The figure shows a tank made up of 3 sections. Cuboid P with a square base of side 14 cm and height 27 cm. Cube Q with a side of 18 cm. Cuboid R that is 72 cm by 19 cm by 44 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 70 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of Q
= 18 x 18 x 18
= 5832 cm³ 

Volume of R
= 72 x 19 x 44
= 60192 cm³ 

2 ℓ = 2000 cm³ 
3.8 ℓ = 3800 cm³ 

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

Height of P to be filled with water
= 70 - (44 + 18)
= 8 cm

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

Volume of water in R, Q and part of P
= 60192 + 5832 + 1568
= 67592 cm³ 

Time taken to reach height
= 67592 ÷ 1800
≈ 38 min (Correct to nearest whole number)

Answer(s): 38 min