A rectangular container measuring 85 cm by 58 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 7 ℓ per minute was first turned on for 3 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 container
= 85 x 58 x 39
= 192270 cm
3 1 ℓ = 1000 cm
3 7 ℓ = 7000 cm
3 Volume of water filled by Tap T
= 7000 x 5
= 35000 cm
3 Volume of water filled by Tap U
= 192270 - 35000
= 157270 cm
3 Rate in which Tap U fills the container
= 157270 ÷ 2
= 78635 cm3/min
78635 mℓ/min
= 78.635 ℓ/min
≈ 78.6 ℓ/min (Correct to 1 decimal place)
Answer(s): 78.6 ℓ/min