A rectangular container measuring 83 cm by 56 cm by 30 cm was to be filled with water by two taps, Q and R. Tap Q which fills the tank at a rate of 6 ℓ per minute was first turned on for 2 minutes before Tap R was turned on as well. If the tank was filled to the brim in a total of 6 minutes from the time when Tap Q was first turned on, what is the rate at which Tap R fills the tank? Give your answer in ℓ per minute correct to 1 decimal place.
Total volume of the container
= 83 x 56 x 30
= 139440 cm
3 1 ℓ = 1000 cm
3 6 ℓ = 6000 cm
3 Volume of water filled by Tap Q
= 6000 x 6
= 36000 cm
3 Volume of water filled by Tap R
= 139440 - 36000
= 103440 cm
3 Rate in which Tap R fills the container
= 103440 ÷ 4
= 25860 cm3/min
25860 mℓ/min
= 25.86 ℓ/min
≈ 25.9 ℓ/min (Correct to 1 decimal place)
Answer(s): 25.9 ℓ/min