A rectangular tank measuring 70 cm by 54 cm by 38 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 2 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 tank
= 70 x 54 x 38
= 143640 cm
3 1 ℓ = 1000 cm
3 5 ℓ = 5000 cm
3 Volume of water filled by Tap B
= 5000 x 6
= 30000 cm
3 Volume of water filled by Tap C
= 143640 - 30000
= 113640 cm
3 Rate in which Tap C fills the tank
= 113640 ÷ 4
= 28410 cm3/min
28410 mℓ/min
= 28.41 ℓ/min
≈ 28.4 ℓ/min (Correct to 1 decimal place)
Answer(s): 28.4 ℓ/min