document.write( "Question 816963: The plane begins his takeoff at 2 PM on a 2500 mile flight. After 5.5 hours, the plane arrived at its destination. Explain why there are at least two different times during the flight when the speed of the plane's 400 mph. \n" ); document.write( "
Algebra.Com's Answer #491811 by TimothyLamb(4379)\"\" \"About 
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average speed:
\n" ); document.write( "2500 / 5.5 = 454.55 mph
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\n" ); document.write( "The problem states that the plane \"begins his takeoff at 2 PM\".
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\n" ); document.write( "Airplanes normally accelerate from full stop to takeoff speed, and then accelerate to cruise speed. Airplanes then decelerate from cruise speed to approach speed, and from approach speed to landing speed.
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\n" ); document.write( "This means that the airplane must have accelerated from 0 to probably well above 454.55 mph to reach its cruise speed, and then decelerated from cruise to well below 454.55 mph for landing.
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\n" ); document.write( "Therefore, the airplane must have flown at 400 mph at least twice during the flight.
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