A rectangular tank measuring 79 cm by 50 cm by 24 cm was to be filled with water by two taps, D and E. Tap D which fills the tank at a rate of 9 ℓ per minute was first turned on for 2 minutes before Tap E was turned on as well. If the tank was filled to the brim in a total of 6 minutes from the time when Tap D was first turned on, what is the rate at which Tap E fills the tank? Give your answer in ℓ per minute correct to 1 decimal place.
Total volume of the tank
= 79 x 50 x 24
= 94800 cm
3 1 ℓ = 1000 cm
3 9 ℓ = 9000 cm
3 Volume of water filled by Tap D
= 9000 x 6
= 54000 cm
3 Volume of water filled by Tap E
= 94800 - 54000
= 40800 cm
3 Rate in which Tap E fills the tank
= 40800 ÷ 4
= 10200 cm3/min
10200 mℓ/min
= 10.2 ℓ/min
≈ 10.2 ℓ/min (Correct to 1 decimal place)
Answer(s): 10.2 ℓ/min