A rectangular container measuring 78 cm by 51 cm by 31 cm was to be filled with water by two taps, C and D. Tap C which fills the tank at a rate of 6 ℓ per minute was first turned on for 4 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 container
= 78 x 51 x 31
= 123318 cm
3 1 ℓ = 1000 cm
3 6 ℓ = 6000 cm
3 Volume of water filled by Tap C
= 6000 x 6
= 36000 cm
3 Volume of water filled by Tap D
= 123318 - 36000
= 87318 cm
3 Rate in which Tap D fills the container
= 87318 ÷ 2
= 43659 cm3/min
43659 mℓ/min
= 43.659 ℓ/min
≈ 43.7 ℓ/min (Correct to 1 decimal place)
Answer(s): 43.7 ℓ/min