document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1183834>Question 1183834</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Hi<BR>\n" );
document.write( "Sally walked halfway to school at 5km per hour. She then ran the rest of the way at 8km per hour. If she rode home at a speed of 40km per hour,what was her average speed to and from school. <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 #814303 by </B><A HREF=/tutors/aboutme.mpl?userid=greenestamps><B>greenestamps(13200)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=greenestamps><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=greenestamps><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=814303\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> <br><BR>\n" );
document.write( "This kind of problem is probably easiest to solve if we choose a \"nice\" number for the distance to the school.  Since the given speeds are 5, 8, and 40km/h, we can choose 40km for the distance to the school.  Note that choice is not reasonable in the real situation -- but it makes solving the problem easy.<br><BR>\n" );
document.write( "She walks half of the 40km at 5km/h, taking 20/5 = 4 hours.<BR>\n" );
document.write( "She walks half of the 40km at 8km/h, taking 20/8 = 2.5 hours.<BR>\n" );
document.write( "She rides back the whole 40km at 40km/h, taking 40/40 = 1 hour.<br><BR>\n" );
document.write( "In all, she traveled 80km in 4+2.5+1 = 7.5 hours; her average speed was 80/7.5 = 160/15 = 32/3km/hr or 10 2/3 km/h.<br><BR>\n" );
document.write( "ANSWER: 10 2/3 km/hr<br><BR>\n" );
document.write( "If you need to solve the problem using formal algebra, simply use d for the distance instead of choosing a specific number.  Then the total time for the trip is<br><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%28d%2F2%29%2F5%2B%28d%2F2%29%2F8%2Bd%2F40+=+d%2F10%2Bd%2F16%2Bd%2F40+=+%288d%2B5d%2B2d%29%2F80+=+15d%2F80+=+3d%2F16 ALIGN=MIDDLE   DISABLED_style= \"max-width:90%; height:auto;\" ><br><BR>\n" );
document.write( "and her average speed was the total distance divided by the total time:<br><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=2d%2F%283d%2F16%29+=+2d%2816%2F3d%29+=+32%2F3 ALIGN=MIDDLE  ALT=\"2d%2F%283d%2F16%29+=+2d%2816%2F3d%29+=+32%2F3\"   DISABLED_style= \"max-width:90%; height:auto;\" ><br><BR>\n" );
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