A rectangular tank measuring 84 cm by 57 cm by 35 cm was to be filled with water by two taps, K and L. Tap K which fills the tank at a rate of 7 ℓ per minute was first turned on for 3 minutes before Tap L was turned on as well. If the tank was filled to the brim in a total of 6 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 57 x 35
= 167580 cm
3 1 ℓ = 1000 cm
3 7 ℓ = 7000 cm
3 Volume of water filled by Tap K
= 7000 x 6
= 42000 cm
3 Volume of water filled by Tap L
= 167580 - 42000
= 125580 cm
3 Rate in which Tap L fills the tank
= 125580 ÷ 3
= 41860 cm3/min
41860 mℓ/min
= 41.86 ℓ/min
≈ 41.9 ℓ/min (Correct to 1 decimal place)
Answer(s): 41.9 ℓ/min