A rectangular tank measuring 80 cm by 60 cm by 25 cm was to be filled with water by two taps, H and J. Tap H which fills the tank at a rate of 7 ℓ per minute was first turned on for 2 minutes before Tap J was turned on as well. If the tank was filled to the brim in a total of 7 minutes from the time when Tap H was first turned on, what is the rate at which Tap J fills the tank? Give your answer in ℓ per minute correct to 1 decimal place.
Total volume of the tank
= 80 x 60 x 25
= 120000 cm
3 1 ℓ = 1000 cm
3 7 ℓ = 7000 cm
3 Volume of water filled by Tap H
= 7000 x 7
= 49000 cm
3 Volume of water filled by Tap J
= 120000 - 49000
= 71000 cm
3 Rate in which Tap J fills the tank
= 71000 ÷ 5
= 14200 cm3/min
14200 mℓ/min
= 14.2 ℓ/min
≈ 14.2 ℓ/min (Correct to 1 decimal place)
Answer(s): 14.2 ℓ/min