A rectangular tank measuring 73 cm by 54 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 7 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 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
= 73 x 54 x 40
= 157680 cm³ 

1 ℓ = 1000 cm³ 
7 ℓ = 7000 cm³ 

Volume of water filled by Tap K
= 7000 x 6
= 42000 cm³

Volume of water filled by Tap L
= 157680 - 42000
= 115680 cm³ 

Rate in which Tap L fills the tank
= 115680 ÷ 2
57840 mℓ/min
= 57.84 ℓ/min
≈ 57.8 ℓ/min (Correct to 1 decimal place)

Answer(s): 57.8 ℓ/min