document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=373648>Question 373648</A>: <I><SPAN STYLE=\"word-break: break-all;\"> I am stuck on how to solve this problem:<BR>\n" );
document.write( "\"I travel from town A to town B, a distance of two miles, at a rate of 30mph. At what speed should I make the return trip so that my average speed for the round trip is 60mph? The answer is NOT 90mph.\"<BR>\n" );
document.write( "How would I go about solving this problem? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #265926 by </B><A HREF=/tutors/aboutme.mpl?userid=josmiceli><B>josmiceli(19441)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=josmiceli><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=josmiceli><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=265926\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> What they are trying to teach you is<BR>\n" );
document.write( "that an average is never an average of<BR>\n" );
document.write( "2 or more averages or a sum of averages. Always go back<BR>\n" );
document.write( "to the basic definition of an average. In this case:<BR>\n" );
document.write( "(average speed) = (total distance travelled)/(total time elapsed)<BR>\n" );
document.write( "The total distance is <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=2+%2B+2+=+4 ALIGN=MIDDLE  ALT=\"2+%2B+2+=+4\"   DISABLED_style= \"max-width:90%; height:auto;\" > mi<BR>\n" );
document.write( "The time for the trip from A to B is <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=2%2F30+=+1%2F15 ALIGN=MIDDLE  ALT=\"2%2F30+=+1%2F15\"   DISABLED_style= \"max-width:90%; height:auto;\" > hr<BR>\n" );
document.write( "Let <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t ALIGN=MIDDLE  ALT=\"t\"   DISABLED_style= \"max-width:90%; height:auto;\" > = the total time<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=4%2Ft+=+60 ALIGN=MIDDLE  ALT=\"4%2Ft+=+60\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=4+=+60t ALIGN=MIDDLE  ALT=\"4+=+60t\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t+=+1%2F15 ALIGN=MIDDLE  ALT=\"t+=+1%2F15\"   DISABLED_style= \"max-width:90%; height:auto;\" > hr<BR>\n" );
document.write( "This tells me that the return tip has to be made in <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=0 ALIGN=MIDDLE  ALT=\"0\"   DISABLED_style= \"max-width:90%; height:auto;\" > hrs,<BR>\n" );
document.write( "and that says that there is no way to average <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=60 ALIGN=MIDDLE  ALT=\"60\"   DISABLED_style= \"max-width:90%; height:auto;\" > mi/hr<BR>\n" );
document.write( "for the round trip.<BR>\n" );
document.write( "Suppose the car was a rocket car and could make the return trip<BR>\n" );
document.write( "in <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=1%2F600000 ALIGN=MIDDLE  ALT=\"1%2F600000\"   DISABLED_style= \"max-width:90%; height:auto;\" > hr<BR>\n" );
document.write( "Now I say that the average speed for the round trip is <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=60 ALIGN=MIDDLE  ALT=\"60\"   DISABLED_style= \"max-width:90%; height:auto;\" > mi/hr<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=4%2F%281%2F15+%2B+2%2F600000%29+=+60 ALIGN=MIDDLE  ALT=\"4%2F%281%2F15+%2B+2%2F600000%29+=+60\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=4%2F%284%2F60+%2B+2%2F600000%29+=+60 ALIGN=MIDDLE  ALT=\"4%2F%284%2F60+%2B+2%2F600000%29+=+60\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=4+=+60%2A%284%2F60+%2B+2%2F600000%29 ALIGN=MIDDLE  ALT=\"4+=+60%2A%284%2F60+%2B+2%2F600000%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=4+=+4+%2B+2%2F10000 ALIGN=MIDDLE  ALT=\"4+=+4+%2B+2%2F10000\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "There's no way to average <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=60 ALIGN=MIDDLE  ALT=\"60\"   DISABLED_style= \"max-width:90%; height:auto;\" > mi/hr<BR>\n" );
document.write( "no matter how fast you make the return trip\r<BR>\n" );
document.write( "\n" );
document.write( " <BR>\n" );
document.write( "  </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );