document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=824576>Question 824576</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Danny drove halfway from town P to town Q at an average speed of 60km/h. He wants to average 80km/h for the entire journey. What will Danny's average speed for the second part of his journey? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #496604 by </B><A HREF=/tutors/aboutme.mpl?userid=Alan3354><B>Alan3354(69443)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Alan3354><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=Alan3354><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=496604\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Danny drove halfway from town P to town Q at an average speed of 60km/h. He wants to average 80km/h for the entire journey. What will Danny's average speed for the second part of his journey?<BR>\n" );
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document.write( "Avg speed for a round trip (or of equal distancts) is<BR>\n" );
document.write( "2*r1*r2/(r1+r2)  (r1 & r2 are the 2 speeds)<BR>\n" );
document.write( "(I can show the derivation if needed)<BR>\n" );
document.write( "2*60*r2/(60+r2) = 80<BR>\n" );
document.write( "60*r2 = 40*60+r2) = 40*r2 + 2400<BR>\n" );
document.write( "20r2 = 2400<BR>\n" );
document.write( "r2 = 120 km/hr<BR>\n" );
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