A rectangular container measuring 74 cm by 50 cm by 35 cm was to be filled with water by two taps, B and C. Tap B which fills the tank at a rate of 5 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 7 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
= 74 x 50 x 35
= 129500 cm
3 1 ℓ = 1000 cm
3 5 ℓ = 5000 cm
3 Volume of water filled by Tap B
= 5000 x 7
= 35000 cm
3 Volume of water filled by Tap C
= 129500 - 35000
= 94500 cm
3 Rate in which Tap C fills the container
= 94500 ÷ 3
= 31500 cm3/min
31500 mℓ/min
= 31.5 ℓ/min
≈ 31.5 ℓ/min (Correct to 1 decimal place)
Answer(s): 31.5 ℓ/min