A rectangular tank measuring 81 cm by 60 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 7 ℓ per minute was first turned on for 3 minutes before Tap C was turned on as well. If the tank was filled to the brim in a total of 5 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 tank
= 81 x 60 x 25
= 121500 cm
3 1 ℓ = 1000 cm
3 7 ℓ = 7000 cm
3 Volume of water filled by Tap B
= 7000 x 5
= 35000 cm
3 Volume of water filled by Tap C
= 121500 - 35000
= 86500 cm
3 Rate in which Tap C fills the tank
= 86500 ÷ 2
= 43250 cm3/min
43250 mℓ/min
= 43.25 ℓ/min
≈ 43.3 ℓ/min (Correct to 1 decimal place)
Answer(s): 43.3 ℓ/min