A rectangular container measuring 78 cm by 51 cm by 31 cm was to be filled with water by two taps, W and X. Tap W which fills the tank at a rate of 7 ℓ per minute was first turned on for 3 minutes before Tap X was turned on as well. If the tank was filled to the brim in a total of 6 minutes from the time when Tap W was first turned on, what is the rate at which Tap X fills the tank? Give your answer in ℓ per minute correct to 1 decimal place.
Total volume of the container
= 78 x 51 x 31
= 123318 cm
3 1 ℓ = 1000 cm
3 7 ℓ = 7000 cm
3 Volume of water filled by Tap W
= 7000 x 6
= 42000 cm
3 Volume of water filled by Tap X
= 123318 - 42000
= 81318 cm
3 Rate in which Tap X fills the container
= 81318 ÷ 3
= 27106 cm3/min
27106 mℓ/min
= 27.106 ℓ/min
≈ 27.1 ℓ/min (Correct to 1 decimal place)
Answer(s): 27.1 ℓ/min