A rectangular container measuring 72 cm by 55 cm by 25 cm was to be filled with water by two taps, B and C. Tap B which fills the tank at a rate of 9 ℓ per minute was first turned on for 4 minutes before Tap C was turned on as well. If the tank was filled to the brim in a total of 6 minutes from the time when Tap B was first turned on, what is the rate at which Tap C fills the tank? Give your answer in ℓ per minute correct to 1 decimal place.
Total volume of the container
= 72 x 55 x 25
= 99000 cm³ 

1 ℓ = 1000 cm³ 
9 ℓ = 9000 cm³ 

Volume of water filled by Tap B
= 9000 x 6
= 54000 cm³

Volume of water filled by Tap C
= 99000 - 54000
= 45000 cm³ 

Rate in which Tap C fills the container
= 45000 ÷ 2
22500 mℓ/min
= 22.5 ℓ/min
≈ 22.5 ℓ/min (Correct to 1 decimal place)

Answer(s): 22.5 ℓ/min