A rectangular container measuring 73 cm by 52 cm by 22 cm was to be filled with water by two taps, P and Q. Tap P which fills the tank at a rate of 7 ℓ per minute was first turned on for 4 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 container
= 73 x 52 x 22
= 83512 cm
3 1 ℓ = 1000 cm
3 7 ℓ = 7000 cm
3 Volume of water filled by Tap P
= 7000 x 6
= 42000 cm
3 Volume of water filled by Tap Q
= 83512 - 42000
= 41512 cm
3 Rate in which Tap Q fills the container
= 41512 ÷ 2
= 20756 cm3/min
20756 mℓ/min
= 20.756 ℓ/min
≈ 20.8 ℓ/min (Correct to 1 decimal place)
Answer(s): 20.8 ℓ/min