A rectangular tank measuring 70 cm by 58 cm by 21 cm was to be filled with water by two taps, C and D. Tap C which fills the tank at a rate of 5 ℓ per minute was first turned on for 3 minutes before Tap D was turned on as well. If the tank was filled to the brim in a total of 5 minutes from the time when Tap C was first turned on, what is the rate at which Tap D fills the tank? Give your answer in ℓ per minute correct to 1 decimal place.
Total volume of the tank
= 70 x 58 x 21
= 85260 cm
3 1 ℓ = 1000 cm
3 5 ℓ = 5000 cm
3 Volume of water filled by Tap C
= 5000 x 5
= 25000 cm
3 Volume of water filled by Tap D
= 85260 - 25000
= 60260 cm
3 Rate in which Tap D fills the tank
= 60260 ÷ 2
= 30130 cm3/min
30130 mℓ/min
= 30.13 ℓ/min
≈ 30.1 ℓ/min (Correct to 1 decimal place)
Answer(s): 30.1 ℓ/min