A rectangular tank measuring 76 cm by 54 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 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 tank
= 76 x 54 x 25
= 102600 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
= 102600 - 42000
= 60600 cm
3 Rate in which Tap Q fills the tank
= 60600 ÷ 2
= 30300 cm3/min
30300 mℓ/min
= 30.3 ℓ/min
≈ 30.3 ℓ/min (Correct to 1 decimal place)
Answer(s): 30.3 ℓ/min