A rectangular container measuring 84 cm by 56 cm by 32 cm was to be filled with water by two taps, D and E. Tap D which fills the tank at a rate of 5 ℓ per minute was first turned on for 3 minutes before Tap E was turned on as well. If the tank was filled to the brim in a total of 7 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 container
= 84 x 56 x 32
= 150528 cm
3 1 ℓ = 1000 cm
3 5 ℓ = 5000 cm
3 Volume of water filled by Tap D
= 5000 x 7
= 35000 cm
3 Volume of water filled by Tap E
= 150528 - 35000
= 115528 cm
3 Rate in which Tap E fills the container
= 115528 ÷ 4
= 28882 cm3/min
28882 mℓ/min
= 28.882 ℓ/min
≈ 28.9 ℓ/min (Correct to 1 decimal place)
Answer(s): 28.9 ℓ/min