document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=204073>Question 204073</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A train goes one way at a speed of x mph and y mph on the return trip. What is its average speed for the trip.<BR>\n" );
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document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #154009 by </B><A HREF=/tutors/aboutme.mpl?userid=RAY100><B>RAY100(1637)</B></A><img src=\"/images/stars/stars-12.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=RAY100><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/images/nopicture.jpg><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=154009\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> velocity  = distance/time,,,or  t=d/v<BR>\n" );
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document.write( ",total  time  =  d/x +d/y =(dy+dx)/xy = d(x+y)/xy<BR>\n" );
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document.write( "total  distance  =2d<BR>\n" );
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document.write( "velocity  total  = total  distance / total time = 2d / {d(x+y)}/xy = 2xy/x+y<BR>\n" );
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document.write( "check,,let  x=50, y=60, d=100  (all  arbitrary)<BR>\n" );
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document.write( "vel = 2(50)(60) / (50 +60) = 6000/110=54.55  mph<BR>\n" );
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document.write( "BIG  NOTE,  it  is  NOT (50 +60) /2 = 55,,,,or  (x+y)/2<BR>\n" );
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document.write( "avg  vel   = distance/time,,,,,,200 / {100/50 +100/60} = 54.55 </SPAN>\n" );
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