A rectangular tank measuring 72 cm by 51 cm by 29 cm was to be filled with water by two taps, W and X. Tap W which fills the tank at a rate of 9 ℓ per minute was first turned on for 4 minutes before Tap X was turned on as well. If the tank was filled to the brim in a total of 7 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 tank
= 72 x 51 x 29
= 106488 cm
3 1 ℓ = 1000 cm
3 9 ℓ = 9000 cm
3 Volume of water filled by Tap W
= 9000 x 7
= 63000 cm
3 Volume of water filled by Tap X
= 106488 - 63000
= 43488 cm
3 Rate in which Tap X fills the tank
= 43488 ÷ 3
= 14496 cm3/min
14496 mℓ/min
= 14.496 ℓ/min
≈ 14.5 ℓ/min (Correct to 1 decimal place)
Answer(s): 14.5 ℓ/min