A rectangular tank measuring 74 cm by 55 cm by 31 cm was to be filled with water by two taps, Z and A. Tap Z which fills the tank at a rate of 6 ℓ per minute was first turned on for 2 minutes before Tap A was turned on as well. If the tank was filled to the brim in a total of 7 minutes from the time when Tap Z was first turned on, what is the rate at which Tap A fills the tank? Give your answer in ℓ per minute correct to 1 decimal place.
Total volume of the tank
= 74 x 55 x 31
= 126170 cm
3 1 ℓ = 1000 cm
3 6 ℓ = 6000 cm
3 Volume of water filled by Tap Z
= 6000 x 7
= 42000 cm
3 Volume of water filled by Tap A
= 126170 - 42000
= 84170 cm
3 Rate in which Tap A fills the tank
= 84170 ÷ 5
= 16834 cm3/min
16834 mℓ/min
= 16.834 ℓ/min
≈ 16.8 ℓ/min (Correct to 1 decimal place)
Answer(s): 16.8 ℓ/min