A rectangular container measuring 79 cm by 57 cm by 35 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 3 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
= 79 x 57 x 35
= 157605 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
= 157605 - 36000
= 121605 cm
3 Rate in which Tap R fills the container
= 121605 ÷ 3
= 40535 cm3/min
40535 mℓ/min
= 40.535 ℓ/min
≈ 40.5 ℓ/min (Correct to 1 decimal place)
Answer(s): 40.5 ℓ/min