document.write( "Question 722530: An airplane takes 3 hours to travel a distance of 1680 miles with the wind. The return trip takes 4 hours against the wind. Find the speed of the plane in still air and the speed of the wind. \n" ); document.write( "
Algebra.Com's Answer #442760 by lwsshak3(11628)\"\" \"About 
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An airplane takes 3 hours to travel a distance of 1680 miles with the wind. The return trip takes 4 hours against the wind. Find the speed of the plane in still air and the speed of the wind.
\n" ); document.write( "***
\n" ); document.write( "let x=speed of plane in still air
\n" ); document.write( "let c=speed of wind
\n" ); document.write( "x+c=speed of plane downwind
\n" ); document.write( "x-c=speed of plane upwind
\n" ); document.write( "travel time=distance/speed
\n" ); document.write( "..
\n" ); document.write( "1680/(x+c)=3
\n" ); document.write( "1680/(x-c)=4
\n" ); document.write( "..
\n" ); document.write( "3x+3c=1680
\n" ); document.write( "4x-4c=1680
\n" ); document.write( "..
\n" ); document.write( "12x+12c=4*1680=6720
\n" ); document.write( "12x-12c=3*1680=5040
\n" ); document.write( "add
\n" ); document.write( "24x=11760
\n" ); document.write( "x=490
\n" ); document.write( "3c=1680-3x
\n" ); document.write( "3c=1680-1470
\n" ); document.write( "3c=210
\n" ); document.write( "c=70
\n" ); document.write( "speed of plane in still air=490 mph
\n" ); document.write( "speed of wind=70 mph \n" ); document.write( "
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