document.write( "Question 889540: A spy plane flies over 600km and back all in six hours and 20 minutes.
\n" ); document.write( "if on the trip, a wind of 10kph was with it and against its return course, what was the speed of the spy plane in still air? \n" ); document.write( "
Algebra.Com's Answer #538254 by lwsshak3(11628)\"\" \"About 
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A spy plane flies over 600km and back all in six hours and 20 minutes.
\n" ); document.write( "if on the trip, a wind of 10kph was with it and against its return course, what was the speed of the spy plane in still air?
\n" ); document.write( "***
\n" ); document.write( "let x=speed of plane in still air
\n" ); document.write( "x+10=speed of plane with wind
\n" ); document.write( "x-10=speed of plane against wind
\n" ); document.write( "travel time=distance/speed
\n" ); document.write( "6 hrs and 20 min=6 1/3 hrs=19/3 hrs
\n" ); document.write( "..
\n" ); document.write( "\"600%2F%28x%2B10%29%2B600%2F%28x-10%29=19%2F3\"
\n" ); document.write( "lcd=(x+10)(x-10)
\n" ); document.write( "(600)(x-10)+600(x+10)=19(x^2-100)/3
\n" ); document.write( "600x-6000+600x+6000=(19x^2-1900)/3
\n" ); document.write( "1200x=(19x^2-1900)/3
\n" ); document.write( "3600x=19x^2-1900
\n" ); document.write( "19x^2-3600x-1900=0
\n" ); document.write( "(x-190)(19x+10)=0 (got this from a graphics program)
\n" ); document.write( "19x+10=0
\n" ); document.write( "x=-10/19(reject)
\n" ); document.write( "or
\n" ); document.write( "x=190
\n" ); document.write( "speed of plane in still air=190 km/hr \n" ); document.write( "
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