document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=791282>Question 791282</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A car travels along a certain road at an average speed of 40 km/h, and returns along the same road at an average speed of 60 km/h. Calculate the average speed for the round trip. (Don't say 50 km/h!) </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #479528 by </B><A HREF=/tutors/aboutme.mpl?userid=jim_thompson5910><B>jim_thompson5910(35256)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=jim_thompson5910><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=479528\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> when the speed is 40 km/hr, we know this much\r<BR>\n" );
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document.write( "d = rt\r<BR>\n" );
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document.write( "d = 40t\r<BR>\n" );
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document.write( "t = d/40\r<BR>\n" );
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document.write( "---------------------\r<BR>\n" );
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document.write( "when the speed is 60 km/hr, we know this much\r<BR>\n" );
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document.write( "d = rt\r<BR>\n" );
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document.write( "d = 60t\r<BR>\n" );
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document.write( "t = d/60\r<BR>\n" );
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document.write( "---------------------\r<BR>\n" );
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document.write( "So it takes d/40 hours when the speed is 40 km/hr and it takes d/60 hours when the speed is 60 km/hr\r<BR>\n" );
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document.write( "Add up the two times\r<BR>\n" );
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document.write( "d/40 + d/60 = 3d/120 + 2d/120\r<BR>\n" );
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document.write( "d/40 + d/60 = 5d/120\r<BR>\n" );
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document.write( "d/40 + d/60 = d/24\r<BR>\n" );
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document.write( "So overall, it will take d/24 hours (for the entire round trip)\r<BR>\n" );
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document.write( "For the sake of simplicity, let's say d = 24 (so that d/24 turns into 24/24 = 1)\r<BR>\n" );
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document.write( "Because going one way will have you going 24 km, this means that completing a full round trip will have you traveling 2*24 = 48 km\r<BR>\n" );
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document.write( "So because you have traveled 48 km in one hour (this is average over the entire trip), the average speed is <font color=\"red\">48 km/hr</font> </SPAN>\n" );
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