A rectangular tank measuring 70 cm by 60 cm by 30 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 2 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
= 70 x 60 x 30
= 126000 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
= 126000 - 63000
= 63000 cm
3 Rate in which Tap U fills the tank
= 63000 ÷ 5
= 12600 cm3/min
12600 mℓ/min
= 12.6 ℓ/min
≈ 12.6 ℓ/min (Correct to 1 decimal place)
Answer(s): 12.6 ℓ/min