A rectangular tank measuring 81 cm by 53 cm by 39 cm was to be filled with water by two taps, T and U. Tap T which fills the tank at a rate of 9 ℓ per minute was first turned on for 4 minutes before Tap U was turned on as well. If the tank was filled to the brim in a total of 5 minutes from the time when Tap T was first turned on, what is the rate at which Tap U fills the tank? Give your answer in ℓ per minute correct to 1 decimal place.
Total volume of the tank
= 81 x 53 x 39
= 167427 cm
3 1 ℓ = 1000 cm
3 9 ℓ = 9000 cm
3 Volume of water filled by Tap T
= 9000 x 5
= 45000 cm
3 Volume of water filled by Tap U
= 167427 - 45000
= 122427 cm
3 Rate in which Tap U fills the tank
= 122427 ÷ 1
= 122427 cm3/min
122427 mℓ/min
= 122.427 ℓ/min
≈ 122.4 ℓ/min (Correct to 1 decimal place)
Answer(s): 122.4 ℓ/min