document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=824528>Question 824528</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Junior drove his rig on Interstate 10 from San Antonio and El Paso.  At the halfway point he noticed that he had been averaging 80 mph, while his company requires his average speed to be 60 mph.  What must be speed for the last half of the trip so that he will average 60 mph for the entire trip.  Distance doesn't matter. </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #496568 by </B><A HREF=/tutors/aboutme.mpl?userid=TimothyLamb><B>TimothyLamb(4379)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=TimothyLamb><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=TimothyLamb><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=496568\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> ---<BR>\n" );
document.write( "s = d / t<BR>\n" );
document.write( "t = d / s<BR>\n" );
document.write( "D = half trip distance<BR>\n" );
document.write( "---<BR>\n" );
document.write( "first half (a):<BR>\n" );
document.write( "t = d / s<BR>\n" );
document.write( "ta = D/80<BR>\n" );
document.write( "---<BR>\n" );
document.write( "second half (b):<BR>\n" );
document.write( "t = d / s<BR>\n" );
document.write( "tb = D/x<BR>\n" );
document.write( "where x is the unknown speed for the second half<BR>\n" );
document.write( "---<BR>\n" );
document.write( "whole trip:<BR>\n" );
document.write( "s = d / t<BR>\n" );
document.write( "60 = 2D / (ta + tb)<BR>\n" );
document.write( "60 = 2D / (D/80 + D/x)<BR>\n" );
document.write( "60(D/80 + D/x) = 2D<BR>\n" );
document.write( "60(xD/80x + 80D/80x) = 2D<BR>\n" );
document.write( "(60D/80x)(x + 80) = 2D<BR>\n" );
document.write( "(60/80x)(x + 80) = 2<BR>\n" );
document.write( "x + 80 = 2*(80/60)x<BR>\n" );
document.write( "x + 80 = (2.666666)x<BR>\n" );
document.write( "(2.666666)x - x = 80<BR>\n" );
document.write( "(1.666666)x = 80<BR>\n" );
document.write( "x = 80/1.666666<BR>\n" );
document.write( "x = 48.0<BR>\n" );
document.write( "---<BR>\n" );
document.write( "answer:<BR>\n" );
document.write( "the speed for the last half of the trip must be: 48 mph<BR>\n" );
document.write( "---<BR>\n" );
document.write( "Solve and graph linear equations:<BR>\n" );
document.write( "https://sooeet.com/math/linear-equation-solver.php<BR>\n" );
document.write( "---<BR>\n" );
document.write( "Solve quadratic equations, quadratic formula:<BR>\n" );
document.write( "https://sooeet.com/math/quadratic-formula-solver.php<BR>\n" );
document.write( "---<BR>\n" );
document.write( "Solve systems of linear equations up to 6-equations 6-variables:<BR>\n" );
document.write( "https://sooeet.com/math/system-of-linear-equations-solver.php </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );