Final answer:
The time it should take for ½ ft³ of gas to turn per revolution when a furnace uses 142.8 ft³/hr is 0.0140 hours or 0.84 minutes. The provided options do not match this calculation, suggesting a possible error in the question or choices.
Step-by-step explanation:
To calculate the time it takes for ½ ft³ of gas to turn per revolution when a furnace is using 142.8 ft³/hr of gas, we divide the volume used per hour by the number of hours in an hour (to find volume per turn) and then find the reciprocal to determine the time for one turn:
Volume per turn = 142.8 ft³/hr ÷ 2 turns/ft³ = 71.4 turns/hr
Time per turn = 1 hr / 71.4 turns = 0.0140 hours or 0.84 minutes
However, none of the given answer choices (A) 0.197 hours, (B) 0.284 hours, (C) 0.352 hours, (D) 0.421 hours match this calculation. There may be a misunderstanding of the problem or a mistake in the given choices.