A rectangular tank measuring 74 cm by 55 cm by 36 cm was to be filled with water by two taps, C and D. Tap C which fills the tank at a rate of 9 ℓ per minute was first turned on for 2 minutes before Tap D was turned on as well. If the tank was filled to the brim in a total of 6 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
= 74 x 55 x 36
= 146520 cm
3 1 ℓ = 1000 cm
3 9 ℓ = 9000 cm
3 Volume of water filled by Tap C
= 9000 x 6
= 54000 cm
3 Volume of water filled by Tap D
= 146520 - 54000
= 92520 cm
3 Rate in which Tap D fills the tank
= 92520 ÷ 4
= 23130 cm3/min
23130 mℓ/min
= 23.13 ℓ/min
≈ 23.1 ℓ/min (Correct to 1 decimal place)
Answer(s): 23.1 ℓ/min