document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=377770>Question 377770</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. -My teacher wrote on the paper that the answer is not 400 MPH. Thank you very much! </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #268433 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=268433\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> I did this one 2 days ago, you can look up the detailed solution on the site.<BR>\n" );
document.write( "---------<BR>\n" );
document.write( "avg speed for the round trip = 2*r1*r2/(rq + r2)<BR>\n" );
document.write( "= 2*380*420/(800)<BR>\n" );
document.write( "= 399 mph\r<BR>\n" );
document.write( "\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );