A rectangular tank measuring 84 cm by 59 cm by 40 cm was to be filled with water by two taps, K and L. Tap K which fills the tank at a rate of 6 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
= 84 x 59 x 40
= 198240 cm
3 1 ℓ = 1000 cm
3 6 ℓ = 6000 cm
3 Volume of water filled by Tap K
= 6000 x 7
= 42000 cm
3 Volume of water filled by Tap L
= 198240 - 42000
= 156240 cm
3 Rate in which Tap L fills the tank
= 156240 ÷ 3
= 52080 cm3/min
52080 mℓ/min
= 52.08 ℓ/min
≈ 52.1 ℓ/min (Correct to 1 decimal place)
Answer(s): 52.1 ℓ/min