A rectangular tank measuring 75 cm by 54 cm by 32 cm was to be filled with water by two taps, P and Q. Tap P which fills the tank at a rate of 9 ℓ per minute was first turned on for 2 minutes before Tap Q was turned on as well. If the tank was filled to the brim in a total of 5 minutes from the time when Tap P was first turned on, what is the rate at which Tap Q fills the tank? Give your answer in ℓ per minute correct to 1 decimal place.
Total volume of the tank
= 75 x 54 x 32
= 129600 cm
3 1 ℓ = 1000 cm
3 9 ℓ = 9000 cm
3 Volume of water filled by Tap P
= 9000 x 5
= 45000 cm
3 Volume of water filled by Tap Q
= 129600 - 45000
= 84600 cm
3 Rate in which Tap Q fills the tank
= 84600 ÷ 3
= 28200 cm3/min
28200 mℓ/min
= 28.2 ℓ/min
≈ 28.2 ℓ/min (Correct to 1 decimal place)
Answer(s): 28.2 ℓ/min