Answer:
The speed of the plane with no wind is 378 miles per hour.
Step-by-step explanation:
Since at maximum speed, an airplane travels 1680 miles against the wind in 5 hours, and flying with the wind. the plane can travel the same distance in 4 hours, to determine what is the speed of the plane with no wind, the following calculation must be performed:
Against the wind = 1680/5 = 336
With the wind = 1680/4 = 420
420 - ((420 - 336) / 2) = X
420 - 42 = X
378 = X
Therefore, the speed of the plane with no wind is 378 miles per hour.
