document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=316576>Question 316576</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A plane can fly 259 miles downwind in the same amount of time as it can travel 161 miles upwind. Find the velocity of the wind, v, if the plane can fly 210 mph in still air.  </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #226465 by </B><A HREF=/tutors/aboutme.mpl?userid=texttutoring><B>texttutoring(324)</B></A><img src=\"/images/stars/stars-10.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=texttutoring><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=texttutoring><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=226465\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> If you're going downwind, you add the wind's velocity (vw) to the plane's still air velocity:\r<BR>\n" );
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document.write( "Downwind:  v = 210+vw\r<BR>\n" );
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document.write( "If you're going upwind, you have to subtract the wind's velocity:\r<BR>\n" );
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document.write( "Upwind: v = 210-vw\r<BR>\n" );
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document.write( "Now use the formula D=VT, where D=distance, v=velocity, and t=time. We know that the times are the same, so isolate for t and set them equal to each other:\r<BR>\n" );
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document.write( "t = d/v\r<BR>\n" );
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document.write( "Dup/Vup = Ddown/Vdown\r<BR>\n" );
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document.write( "161/(210-vw) = 259/(210+vw)\r<BR>\n" );
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document.write( "Now cross multiply and solve for vw:\r<BR>\n" );
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document.write( "33810 +161vw = 54390 -259vw<BR>\n" );
document.write( "420vw = 20580<BR>\n" );
document.write( "vw=49\r<BR>\n" );
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document.write( "The wind's velocity is 49mph. </SPAN>\n" );
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