document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=938308>Question 938308</A>: <I><SPAN STYLE=\"word-break: break-all;\"> This problem has two weird aspects:  One, it gives what appears to be a rate with no per hour, per minute.  The other is it flies twice as fast with the wind but takes the same amount of time to cover the same territory as when flying half as fast against the wind.  NOT POSSIBLE.  But for your reading enjoyment . . .\r<BR>\n" );
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document.write( "\"A bird takes 45 min to make a 480 m round trip between two trees.  Flying 0.25 m against the wind on the first half takes the same time as flying 0.5 m with the wind on the return flight.  Find the rate of the bird in calm conditions and the rate of the wind.\" </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #571575 by </B><A HREF=/tutors/aboutme.mpl?userid=Alan3354><B>Alan3354(69443)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Alan3354><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=Alan3354><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=571575\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> \"A bird takes 45 min to make a 480 m round trip between two trees.  Flying 0.25 m against the wind on the first half takes the same time as flying 0.5 m with the wind on the return flight.  Find the rate of the bird in calm conditions and the rate of the wind.\"<BR>\n" );
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document.write( "It's flying 2x as fast downwind as upwind (its groundspeed)<BR>\n" );
document.write( "Call r its upwind groundspeed --> 2r downwind.<BR>\n" );
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document.write( "The round trip avg speed = 2*r*2r/(r + 2r) = 4r/3<BR>\n" );
document.write( "The round trip avg speed = d/t = 480/(3/4) = 640 m/hr<BR>\n" );
document.write( "4r/3 = 640<BR>\n" );
document.write( "r = 480 m/hr upwind<BR>\n" );
document.write( "downwind speed = 2r = 960 m/hr<BR>\n" );
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document.write( "The bird's airspeed is the average of upwind & downwind groundspeeds<BR>\n" );
document.write( "= 720 m/hr<BR>\n" );
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document.write( "windspeed is the difference between airspeed & groundspeed = 240 m/hr </SPAN>\n" );
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