A rectangular tank measuring 77 cm by 54 cm by 33 cm was to be filled with water by two taps, K and L. Tap K which fills the tank at a rate of 9 ℓ per minute was first turned on for 4 minutes before Tap L was turned on as well. If the tank was filled to the brim in a total of 7 minutes from the time when Tap K was first turned on, what is the rate at which Tap L fills the tank? Give your answer in ℓ per minute correct to 1 decimal place.
Total volume of the tank
= 77 x 54 x 33
= 137214 cm
3 1 ℓ = 1000 cm
3 9 ℓ = 9000 cm
3 Volume of water filled by Tap K
= 9000 x 7
= 63000 cm
3 Volume of water filled by Tap L
= 137214 - 63000
= 74214 cm
3 Rate in which Tap L fills the tank
= 74214 ÷ 3
= 24738 cm3/min
24738 mℓ/min
= 24.738 ℓ/min
≈ 24.7 ℓ/min (Correct to 1 decimal place)
Answer(s): 24.7 ℓ/min