A rectangular tank measuring 78 cm by 59 cm by 34 cm was to be filled with water by two taps, M and N. Tap M which fills the tank at a rate of 9 ℓ per minute was first turned on for 3 minutes before Tap N was turned on as well. If the tank was filled to the brim in a total of 6 minutes from the time when Tap M was first turned on, what is the rate at which Tap N fills the tank? Give your answer in ℓ per minute correct to 1 decimal place.
Total volume of the tank
= 78 x 59 x 34
= 156468 cm
3 1 ℓ = 1000 cm
3 9 ℓ = 9000 cm
3 Volume of water filled by Tap M
= 9000 x 6
= 54000 cm
3 Volume of water filled by Tap N
= 156468 - 54000
= 102468 cm
3 Rate in which Tap N fills the tank
= 102468 ÷ 3
= 34156 cm3/min
34156 mℓ/min
= 34.156 ℓ/min
≈ 34.2 ℓ/min (Correct to 1 decimal place)
Answer(s): 34.2 ℓ/min