A rectangular container measuring 72 cm by 50 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 2 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 container
= 72 x 50 x 31
= 111600 cm
3 1 ℓ = 1000 cm
3 7 ℓ = 7000 cm
3 Volume of water filled by Tap W
= 7000 x 7
= 49000 cm
3 Volume of water filled by Tap X
= 111600 - 49000
= 62600 cm
3 Rate in which Tap X fills the container
= 62600 ÷ 5
= 12520 cm3/min
12520 mℓ/min
= 12.52 ℓ/min
≈ 12.5 ℓ/min (Correct to 1 decimal place)
Answer(s): 12.5 ℓ/min