document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=778647>Question 778647</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A homing device left its home to deliver a message. On takeoff the device encountered a tailwind of 9 mph and made the delivery in 20 minutes. The return trip into the wind took 40 minutes. How fast could the device fly 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 #474868 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=474868\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> A homing device left its home to deliver a message.<BR>\n" );
document.write( " On takeoff the device encountered a tailwind of 9 mph and made the delivery in 20 minutes.<BR>\n" );
document.write( " The return trip into the wind took 40 minutes.<BR>\n" );
document.write( " How fast could the device fly in still air?<BR>\n" );
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document.write( "Let s = speed in still air<BR>\n" );
document.write( "then<BR>\n" );
document.write( "(s+9) = relative speed with the wind<BR>\n" );
document.write( "and<BR>\n" );
document.write( "(s-9) = relative speed against<BR>\n" );
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document.write( "Change 20 min to 1/3 hr. Change 40 min to 2/3 hr<BR>\n" );
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document.write( "Write a distance equation, distance there and back are the same<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=2%2F3 ALIGN=MIDDLE  ALT=\"2%2F3\"   DISABLED_style= \"max-width:90%; height:auto;\" >(s-9) = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=1%2F3 ALIGN=MIDDLE  ALT=\"1%2F3\"   DISABLED_style= \"max-width:90%; height:auto;\" >(s+9)<BR>\n" );
document.write( "multiply both sides by 3, resulting in:<BR>\n" );
document.write( "2(s-9) = s + 9<BR>\n" );
document.write( "2s - 18 = s + 9<BR>\n" );
document.write( "2s -s = 9 + 18<BR>\n" );
document.write( "s = 27 mph speed in still air<BR>\n" );
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document.write( "Confirm this by finding the actual distances<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=2%2F3 ALIGN=MIDDLE  ALT=\"2%2F3\"   DISABLED_style= \"max-width:90%; height:auto;\" >*(27-9) = 12 mi<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=1%2F3 ALIGN=MIDDLE  ALT=\"1%2F3\"   DISABLED_style= \"max-width:90%; height:auto;\" >*(27+9) = 12 mi </SPAN>\n" );
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