document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1039246>Question 1039246</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A plane travels at a speed of 160 mph in still air. Flying with a tailwind the plane is clocked over a distance of 800 miles. Flying against a headwind, it takes 3 hours longer to complete the return trip. What was the wind velocity? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #653989 by </B><A HREF=/tutors/aboutme.mpl?userid=ankor@dixie-net.com><B>ankor@dixie-net.com(22740)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=ankor@dixie-net.com><IMG SRC=http://www.algebra.com/images/aboutme-small.gif BORDER=0 alt=\"About Me\" VALIGN=MIDDLE></A>&nbsp;<IMG SRC=http://www.algebra.com/cgi-bin/show-face.mpl?user=ankor@dixie-net.com><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=653989\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\">  A plane travels at a speed of 160 mph in still air.<BR>\n" );
document.write( " Flying with a tailwind the plane is clocked over a distance of 800 miles.<BR>\n" );
document.write( " Flying against a headwind, it takes 3 hours longer to complete the return trip.<BR>\n" );
document.write( " What was the wind velocity?<BR>\n" );
document.write( ":<BR>\n" );
document.write( "let w = the velocity of the wind<BR>\n" );
document.write( "then<BR>\n" );
document.write( "(160+w) = the effective speed with the wind<BR>\n" );
document.write( "and<BR>\n" );
document.write( "(160-w) = the effective speed against <BR>\n" );
document.write( ":<BR>\n" );
document.write( "Write a time equation; time = dist/speed<BR>\n" );
document.write( "Against time - with time = 3 hr<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=800%2F%28%28160-w%29%29 ALIGN=MIDDLE  ALT=\"800%2F%28%28160-w%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > - <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=800%2F%28%28160%2Bw%29%29 ALIGN=MIDDLE  ALT=\"800%2F%28%28160%2Bw%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > = 3<BR>\n" );
document.write( "Multiply equation by (160-w)(160+w), cancel the denominators<BR>\n" );
document.write( "800(160+w) - 800(160-w) = 3(160-w)(160+w)<BR>\n" );
document.write( "128000 + 800w - 128000 + 800w = 3(25600-w^2)<BR>\n" );
document.write( "1600w = 76800 - 3w^2<BR>\n" );
document.write( "Form a quadratic equation on the left<BR>\n" );
document.write( "3w^2 + 1600w - 76800 = 0<BR>\n" );
document.write( "Use the quadratic formula to find w: a=3; b=1600; c=-76800<BR>\n" );
document.write( "I got a positive solution of<BR>\n" );
document.write( "w = 44.32 mph is the speed of the wind<BR>\n" );
document.write( ":<BR>\n" );
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document.write( "Check this by finding the actual time each way<BR>\n" );
document.write( "800/(160-44.32) = 6.915 hrs<BR>\n" );
document.write( "800/(160+44.32) = 3.915 hrs<BR>\n" );
document.write( "----------------------------<BR>\n" );
document.write( "travel time diff: 3 hrs<BR>\n" );
document.write( " </SPAN>\n" );
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