A rectangular container measuring 89 cm by 58 cm by 20 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 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 container
= 89 x 58 x 20
= 103240 cm
3 1 ℓ = 1000 cm
3 8 ℓ = 8000 cm
3 Volume of water filled by Tap P
= 8000 x 5
= 40000 cm
3 Volume of water filled by Tap Q
= 103240 - 40000
= 63240 cm
3 Rate in which Tap Q fills the container
= 63240 ÷ 3
= 21080 cm3/min
21080 mℓ/min
= 21.08 ℓ/min
≈ 21.1 ℓ/min (Correct to 1 decimal place)
Answer(s): 21.1 ℓ/min