document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=260796>Question 260796</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A car travels up a hill at a constant speed of 36 km/h and returns down the hill at a constant speed of 70 km/h. Calculate the average speed (in km/h) for the round trip. \r<BR>\n" );
document.write( "\n" );
document.write( " </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #192133 by </B><A HREF=/tutors/aboutme.mpl?userid=ankor@dixie-net.com><B>ankor@dixie-net.com(22740)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=ankor@dixie-net.com><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=ankor@dixie-net.com><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=192133\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> A car travels up a hill at a constant speed of 36 km/h and returns down the hill at a constant speed of 70 km/h.<BR>\n" );
document.write( " Calculate the average speed (in km/h) for the round trip.<BR>\n" );
document.write( ":<BR>\n" );
document.write( "Let s = average speed for the round trip<BR>\n" );
document.write( "Let d = distance one way; <BR>\n" );
document.write( "write a time equation: time = dist/speed<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=d%2F36 ALIGN=MIDDLE  ALT=\"d%2F36\"   DISABLED_style= \"max-width:90%; height:auto;\" > + <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=d%2F70 ALIGN=MIDDLE  ALT=\"d%2F70\"   DISABLED_style= \"max-width:90%; height:auto;\" > = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%282d%29%2Fs ALIGN=MIDDLE  ALT=\"%282d%29%2Fs\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "Multiply equation by by 2520s (36*70) to get rid of the denominators, results:<BR>\n" );
document.write( "70ds + 36ds = 2520(2d)<BR>\n" );
document.write( "106ds = 5040d<BR>\n" );
document.write( "Divide both sides by d<BR>\n" );
document.write( "106s = 5040<BR>\n" );
document.write( "s = 5040/106<BR>\n" );
document.write( "s = 47.5 km/hr, average speed for the round trip<BR>\n" );
document.write( "  </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );