A rectangular tank measuring 90 cm by 59 cm by 20 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 tank
= 90 x 59 x 20
= 106200 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
= 106200 - 45000
= 61200 cm
3 Rate in which Tap P fills the tank
= 61200 ÷ 1
= 61200 cm3/min
61200 mℓ/min
= 61.2 ℓ/min
≈ 61.2 ℓ/min (Correct to 1 decimal place)
Answer(s): 61.2 ℓ/min