A rectangular tank measuring 83 cm by 52 cm by 30 cm was to be filled with water by two taps, J and K. Tap J which fills the tank at a rate of 9 ℓ per minute was first turned on for 4 minutes before Tap K was turned on as well. If the tank was filled to the brim in a total of 5 minutes from the time when Tap J was first turned on, what is the rate at which Tap K fills the tank? Give your answer in ℓ per minute correct to 1 decimal place.
Total volume of the tank
= 83 x 52 x 30
= 129480 cm
3 1 ℓ = 1000 cm
3 9 ℓ = 9000 cm
3 Volume of water filled by Tap J
= 9000 x 5
= 45000 cm
3 Volume of water filled by Tap K
= 129480 - 45000
= 84480 cm
3 Rate in which Tap K fills the tank
= 84480 ÷ 1
= 84480 cm3/min
84480 mℓ/min
= 84.48 ℓ/min
≈ 84.5 ℓ/min (Correct to 1 decimal place)
Answer(s): 84.5 ℓ/min