document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=252822>Question 252822</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Flying east between two cities, a plane's speed is 380 mph.  On the return trip it flies at 420 mph.  Find the average speed over the whole round trip.  (NO, the answer is not 400 mph.) </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #184924 by </B><A HREF=/tutors/aboutme.mpl?userid=richwmiller><B>richwmiller(17219)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=richwmiller><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=richwmiller><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=184924\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> No, it isn't 400 but the difference is not worth the bother. I doubt the speedometers are that accurate anyways, especially if they are analog.\r<BR>\n" );
document.write( "\n" );
document.write( "r=distance/time<BR>\n" );
document.write( "time=d/380+d/420<BR>\n" );
document.write( "distance=2d<BR>\n" );
document.write( "r=2d/(d/380+d/420)<BR>\n" );
document.write( "r=399 </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );