A rectangular tank measuring 83 cm by 60 cm by 25 cm was to be filled with water by two taps, P and Q. Tap P which fills the tank at a rate of 8 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 6 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
= 83 x 60 x 25
= 124500 cm
3 1 ℓ = 1000 cm
3 8 ℓ = 8000 cm
3 Volume of water filled by Tap P
= 8000 x 6
= 48000 cm
3 Volume of water filled by Tap Q
= 124500 - 48000
= 76500 cm
3 Rate in which Tap Q fills the tank
= 76500 ÷ 4
= 19125 cm3/min
19125 mℓ/min
= 19.125 ℓ/min
≈ 19.1 ℓ/min (Correct to 1 decimal place)
Answer(s): 19.1 ℓ/min