A rectangular container measuring 84 cm by 50 cm by 31 cm was to be filled with water by two taps, U and V. Tap U which fills the tank at a rate of 9 ℓ per minute was first turned on for 3 minutes before Tap V was turned on as well. If the tank was filled to the brim in a total of 7 minutes from the time when Tap U was first turned on, what is the rate at which Tap V fills the tank? Give your answer in ℓ per minute correct to 1 decimal place.
Total volume of the container
= 84 x 50 x 31
= 130200 cm
3 1 ℓ = 1000 cm
3 9 ℓ = 9000 cm
3 Volume of water filled by Tap U
= 9000 x 7
= 63000 cm
3 Volume of water filled by Tap V
= 130200 - 63000
= 67200 cm
3 Rate in which Tap V fills the container
= 67200 ÷ 4
= 16800 cm3/min
16800 mℓ/min
= 16.8 ℓ/min
≈ 16.8 ℓ/min (Correct to 1 decimal place)
Answer(s): 16.8 ℓ/min