A rectangular container measuring 85 cm by 58 cm by 24 cm was to be filled with water by two taps, Y and Z. Tap Y which fills the tank at a rate of 5 ℓ per minute was first turned on for 3 minutes before Tap Z was turned on as well. If the tank was filled to the brim in a total of 7 minutes from the time when Tap Y was first turned on, what is the rate at which Tap Z fills the tank? Give your answer in ℓ per minute correct to 1 decimal place.
Total volume of the container
= 85 x 58 x 24
= 118320 cm
3 1 ℓ = 1000 cm
3 5 ℓ = 5000 cm
3 Volume of water filled by Tap Y
= 5000 x 7
= 35000 cm
3 Volume of water filled by Tap Z
= 118320 - 35000
= 83320 cm
3 Rate in which Tap Z fills the container
= 83320 ÷ 4
= 20830 cm3/min
20830 mℓ/min
= 20.83 ℓ/min
≈ 20.8 ℓ/min (Correct to 1 decimal place)
Answer(s): 20.8 ℓ/min