A rectangular container measuring 77 cm by 54 cm by 30 cm was to be filled with water by two taps, N and P. Tap N which fills the tank at a rate of 9 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 5 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
= 77 x 54 x 30
= 124740 cm
3 1 ℓ = 1000 cm
3 9 ℓ = 9000 cm
3 Volume of water filled by Tap N
= 9000 x 5
= 45000 cm
3 Volume of water filled by Tap P
= 124740 - 45000
= 79740 cm
3 Rate in which Tap P fills the container
= 79740 ÷ 1
= 79740 cm3/min
79740 mℓ/min
= 79.74 ℓ/min
≈ 79.7 ℓ/min (Correct to 1 decimal place)
Answer(s): 79.7 ℓ/min