A rectangular tank measuring 72 cm by 54 cm by 34 cm was to be filled with water by two taps, S and T. Tap S which fills the tank at a rate of 9 ℓ per minute was first turned on for 4 minutes before Tap T was turned on as well. If the tank was filled to the brim in a total of 7 minutes from the time when Tap S was first turned on, what is the rate at which Tap T fills the tank? Give your answer in ℓ per minute correct to 1 decimal place.
Total volume of the tank
= 72 x 54 x 34
= 132192 cm
3 1 ℓ = 1000 cm
3 9 ℓ = 9000 cm
3 Volume of water filled by Tap S
= 9000 x 7
= 63000 cm
3 Volume of water filled by Tap T
= 132192 - 63000
= 69192 cm
3 Rate in which Tap T fills the tank
= 69192 ÷ 3
= 23064 cm3/min
23064 mℓ/min
= 23.064 ℓ/min
≈ 23.1 ℓ/min (Correct to 1 decimal place)
Answer(s): 23.1 ℓ/min