A rectangular container measuring 72 cm by 57 cm by 40 cm was to be filled with water by two taps, N and P. Tap N which fills the tank at a rate of 7 ℓ per minute was first turned on for 4 minutes before Tap P was turned on as well. If the tank was filled to the brim in a total of 6 minutes from the time when Tap N was first turned on, what is the rate at which Tap P fills the tank? Give your answer in ℓ per minute correct to 1 decimal place.
Total volume of the container
= 72 x 57 x 40
= 164160 cm
3 1 ℓ = 1000 cm
3 7 ℓ = 7000 cm
3 Volume of water filled by Tap N
= 7000 x 6
= 42000 cm
3 Volume of water filled by Tap P
= 164160 - 42000
= 122160 cm
3 Rate in which Tap P fills the container
= 122160 ÷ 2
= 61080 cm3/min
61080 mℓ/min
= 61.08 ℓ/min
≈ 61.1 ℓ/min (Correct to 1 decimal place)
Answer(s): 61.1 ℓ/min