A rectangular tank measuring 79 cm by 59 cm by 22 cm was to be filled with water by two taps, T and U. Tap T which fills the tank at a rate of 6 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
= 79 x 59 x 22
= 102542 cm
3 1 ℓ = 1000 cm
3 6 ℓ = 6000 cm
3 Volume of water filled by Tap T
= 6000 x 5
= 30000 cm
3 Volume of water filled by Tap U
= 102542 - 30000
= 72542 cm
3 Rate in which Tap U fills the tank
= 72542 ÷ 1
= 72542 cm3/min
72542 mℓ/min
= 72.542 ℓ/min
≈ 72.5 ℓ/min (Correct to 1 decimal place)
Answer(s): 72.5 ℓ/min