A rectangular tank measuring 80 cm by 55 cm by 24 cm was to be filled with water by two taps, C and D. Tap C which fills the tank at a rate of 7 ℓ per minute was first turned on for 3 minutes before Tap D was turned on as well. If the tank was filled to the brim in a total of 7 minutes from the time when Tap C was first turned on, what is the rate at which Tap D fills the tank? Give your answer in ℓ per minute correct to 1 decimal place.
Total volume of the tank
= 80 x 55 x 24
= 105600 cm
3 1 ℓ = 1000 cm
3 7 ℓ = 7000 cm
3 Volume of water filled by Tap C
= 7000 x 7
= 49000 cm
3 Volume of water filled by Tap D
= 105600 - 49000
= 56600 cm
3 Rate in which Tap D fills the tank
= 56600 ÷ 4
= 14150 cm3/min
14150 mℓ/min
= 14.15 ℓ/min
≈ 14.2 ℓ/min (Correct to 1 decimal place)
Answer(s): 14.2 ℓ/min