Question

A plane begins its takeoff at 2:00 pm on a 2500-mile flight. The plane arrives at its destination at 7:30 pm (ignore time zone changes). Explain why there were at least two times during the flight when the speed of the plane was 400 miles per hour.

Answer 1

From the average speed we can analyze that the plane must have reached the speed of 454.54 or more at least once during the journey

this also concludes that the plane must have reached the speed of 400 miles per hour once while reaching to the average speed after the takeoff

Also,

During the arrival the speed of the plane also reached went from the average speed to 400 miles per hour and then zero at the arrival destination

Explanation:

Data provided in the question:

Total distance of the flight = 2500 miles

Flight takeoff time = 2:00 pm

Arrival time of the flight = 7:30 pm

Therefore,

The total time taken by the flight to cover 2500 = 5 hours 30 minutes

= 5.5 hours

Thus,

Average speed of the plane =
`\frac{\textup{Total distance}}{\textup{Total time}}`

or

Average speed of the plane =
`\frac{\textup{2500}}{\textup{5.5}}`

or

Average speed of the plane = 454.54 miles per hour

From the average speed we can analyze that the plane must have reached the speed of 454.54 or more at least once during the journey

this also concludes that the plane must have reached the speed of 400 miles per hour once while reaching to the average speed after the takeoff

Also,

During the arrival the speed of the plane also reached went from the average speed to 400 miles per hour and then zero at the arrival destination

Hence,

the here were at least two times during the flight when the speed of the plane was 400 miles per hour