A rectangular tank measuring 90 cm by 55 cm by 36 cm was to be filled with water by two taps, P and Q. Tap P which fills the tank at a rate of 5 ℓ per minute was first turned on for 3 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
= 90 x 55 x 36
= 178200 cm
3 1 ℓ = 1000 cm
3 5 ℓ = 5000 cm
3 Volume of water filled by Tap P
= 5000 x 5
= 25000 cm
3 Volume of water filled by Tap Q
= 178200 - 25000
= 153200 cm
3 Rate in which Tap Q fills the tank
= 153200 ÷ 2
= 76600 cm3/min
76600 mℓ/min
= 76.6 ℓ/min
≈ 76.6 ℓ/min (Correct to 1 decimal place)
Answer(s): 76.6 ℓ/min