The figure, not drawn to scale, shows an empty tank measuring 20 cm by 15 cm by 25 cm. Water flows from Tap P at a rate of 400 mℓ per minute and from Tap Q at a rate of 180 mℓ per minute. Tower R and Tower S have a base area of 50 cm² and 60 cm² respectively. Water is drained out of the container at a rate of 110 mℓ per minute. Find the height of the water level after 19 minutes.
Volume of the tank
= 20 x 15 x 25
= 7500 cm³ 

Volume of water flow per minute
= 400 + 180 - 110
= 470 cm³/min

Volume of water flow in 19 minutes
= 19 x 470
= 8930 cm³ 

Volume of water in the 2 towers
= 8930 - 7500
= 1430 cm³ 

Total combined base areas of 2 towers
= 50 + 60
= 110 cm² 

Height of water in 2 towers
= 1430 ÷ 110
= 13 cm

Total height of water
= 13 + 25
= 38 cm

Answer(s): 38 cm