document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=78171>Question 78171</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A plane flies 720 mi against a steady 30 mi/h headwind and then returns to the same point with the wind.  If the entire trip takes 10 hours, what is the plane's speed still in the air? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #56078 by </B><A HREF=/tutors/aboutme.mpl?userid=scott8148><B>scott8148(6628)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=scott8148><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=scott8148><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=56078\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> let s=speed in still air ... (rate)*(time)=distance so t=d/r ... (time out)+(time back)=(total time)\r<BR>\n" );
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document.write( "(720/(s-30))+(720/(s+30))=10 ... multiplying by <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=s%5E2-900 ALIGN=MIDDLE  ALT=\"s%5E2-900\"   DISABLED_style= \"max-width:90%; height:auto;\" > and dividing by 10 gives <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=72%28s%2B30%29%2B72%28s-30%29=s%5E2-900 ALIGN=MIDDLE  ALT=\"72%28s%2B30%29%2B72%28s-30%29=s%5E2-900\"   DISABLED_style= \"max-width:90%; height:auto;\" >\r<BR>\n" );
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document.write( "distributing and rearranging terms gives <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=s%5E2-144s-900=0 ALIGN=MIDDLE  ALT=\"s%5E2-144s-900=0\"   DISABLED_style= \"max-width:90%; height:auto;\" > ... factoring gives (s-150)(s+6)=0 ... so s=150 mi/h </SPAN>\n" );
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