A rectangular tank measuring 81 cm by 52 cm by 34 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 7 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 52 x 34
= 143208 cm
3 1 ℓ = 1000 cm
3 9 ℓ = 9000 cm
3 Volume of water filled by Tap T
= 9000 x 7
= 63000 cm
3 Volume of water filled by Tap U
= 143208 - 63000
= 80208 cm
3 Rate in which Tap U fills the tank
= 80208 ÷ 3
= 26736 cm3/min
26736 mℓ/min
= 26.736 ℓ/min
≈ 26.7 ℓ/min (Correct to 1 decimal place)
Answer(s): 26.7 ℓ/min