document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=623037>Question 623037</A>: <I><SPAN STYLE=\"word-break: break-all;\"> an airplane makes a 990 km flight with a tailwind and returns, flying into the same wind.The total flying time is 3hrs 20 mins and the airplanes speed in still air is600 km/h<BR>\n" );
document.write( "what is the speed of the wind.<BR>\n" );
document.write( " I have the total distance travelled to be 990+990=1980<BR>\n" );
document.write( "Total time 200 min rtn or 100 min each way\r<BR>\n" );
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document.write( "Then I am stuck </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #391789 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=391789\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> an airplane makes a 990 km flight with a tailwind and returns, flying into the same wind.The total flying time is 3hrs 20 mins and the airplanes speed in still air is600 km/h<BR>\n" );
document.write( "what is the speed of the wind.<BR>\n" );
document.write( " I have the total distance travelled to be 990+990=1980<BR>\n" );
document.write( "Total time 200 min rtn or 100 min each way<BR>\n" );
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document.write( "It's not 100 mins each way.  Downwind ground speed is greater than upwind.<BR>\n" );
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document.write( "d = distance one way<BR>\n" );
document.write( "d/(600 + w) + d/(600 - w) = 10/3 hours<BR>\n" );
document.write( "990/(600 + w) + 990/(600 - w) = 10/3 hours<BR>\n" );
document.write( "Multiply by 3*(660 + w)*(600 - w)<BR>\n" );
document.write( "2970*(600 - w) + 2970*(600 + w) = 10*(600 + w)*(600 - w)<BR>\n" );
document.write( "297*1200 = 360000 - w^2<BR>\n" );
document.write( "w^2 = 360000 - 356400 = 3600<BR>\n" );
document.write( "w = 60 km/hr </SPAN>\n" );
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