A rectangular tank measuring 81 cm by 50 cm by 22 cm was to be filled with water by two taps, L and M. Tap L which fills the tank at a rate of 8 ℓ per minute was first turned on for 3 minutes before Tap M was turned on as well. If the tank was filled to the brim in a total of 7 minutes from the time when Tap L was first turned on, what is the rate at which Tap M fills the tank? Give your answer in ℓ per minute correct to 1 decimal place.
Total volume of the tank
= 81 x 50 x 22
= 89100 cm
3 1 ℓ = 1000 cm
3 8 ℓ = 8000 cm
3 Volume of water filled by Tap L
= 8000 x 7
= 56000 cm
3 Volume of water filled by Tap M
= 89100 - 56000
= 33100 cm
3 Rate in which Tap M fills the tank
= 33100 ÷ 4
= 8275 cm3/min
8275 mℓ/min
= 8.275 ℓ/min
≈ 8.3 ℓ/min (Correct to 1 decimal place)
Answer(s): 8.3 ℓ/min