document.write( "Question 250640: A pilot wants to make an 840-mile round trip from Cleveland to Peoria and back in 5 hours flying time. There will be a headwind of 30 mph going to Peoria and it is estimated that there will be a 40 mph tailwind returning to Cleveland. At what constant engine speed should the plane be flown? \n" ); document.write( "
Algebra.Com's Answer #182632 by checkley77(12844)\"\" \"About 
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D=RT
\n" ); document.write( "840/2=420 MILES EACH TRIP.
\n" ); document.write( "420=(R-30)T THE TRIP TO PEORIA.
\n" ); document.write( "T=420/(R-30) REPLACE T BY (420/(R-30) IN THE NEXT EQUATION.
\n" ); document.write( "420=(R+40)(5-T) THE RETURN TRIP.
\n" ); document.write( "420=(R+40)(5-(420/(R-30)))
\n" ); document.write( "420=(R+40)(5R-150-420)/(R-30)
\n" ); document.write( "420=(R+40)(5R-570)/(R-30)
\n" ); document.write( "420(R-30)=(R+40)(5R-570)
\n" ); document.write( "420R-12,600=5R^2-370R-22,800
\n" ); document.write( "5R^2-370R-420R-22,800+12,600=0
\n" ); document.write( "5R^2-790R-10,200=0
\n" ); document.write( "5(R^2-158R-2,040)=0
\n" ); document.write( "5(R-170)(R+12)=0
\n" ); document.write( "R-170=0
\n" ); document.write( "R=170 SPEED OF THE PLSNE .
\n" ); document.write( "PROOF:
\n" ); document.write( "420=(170-30)T
\n" ); document.write( "420=140T
\n" ); document.write( "T=420/140
\n" ); document.write( "T=3 HOURS FOR THE FIRST TRIP.
\n" ); document.write( "420=(170+40)(5-3)
\n" ); document.write( "420=210*2
\n" ); document.write( "420=420 \n" ); document.write( "
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