document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=551362>Question 551362</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A car travels from A to B at a speed of 40mph and returns from B to A at 60mph. What is the average for the round trip?\r<BR>\n" );
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document.write( "It says that the answer is 48mph, but I don't understand why. It seems logical for the answer to be 50mph. However, I'm obviously missing something. Could you please explain in a simple and understandable way? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #359682 by </B><A HREF=/tutors/aboutme.mpl?userid=fcabanski><B>fcabanski(1391)</B></A><img src=\"/images/stars/stars-12.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=fcabanski><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=359682\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> The average speed for the whole trip is the total distance traveled divided by the total time it took to travel that distance.<P><BR>\n" );
document.write( "Distance = Rate * Time<P><BR>\n" );
document.write( "The distance in both cases is the same, the rates are different and the times are different.<P><BR>\n" );
document.write( "Call the time for A to B t and the time for B to A T<BR>\n" );
document.write( "For A to B distance = 40t and for B to A the distance = 60T<BR>\n" );
document.write( "The average speed for the trip is then (40t+60T)/(T+t)<P><BR>\n" );
document.write( "Since the distances are the same we know 40t=60T and thus t = 60/40 * T = (3/2)T.<P><BR>\n" );
document.write( "So the average speed is (40*(3/2)T + 60T)/(T+(3/2)T = 120T/(5/2)T = 120*2/5 = 48 MPH<BR>\n" );
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