document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=819277>Question 819277</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Need help setting up the equation \r<BR>\n" );
document.write( "\n" );
document.write( "Tina is training for a biathlon. To train for the running portion of the race, she runs 10 miles each day, over the same course. The first 4 miles of the course is on level ground, while the last 6 miles is downhill. She runs 4 miles per hour slower on level ground than she runs downhill. If the complete course takes 1 hour, how fast does she run on the downhill part of the course?  </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #493002 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=493002\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> s = d / t<BR>\n" );
document.write( "t = d / s<BR>\n" );
document.write( "---<BR>\n" );
document.write( "level time:<BR>\n" );
document.write( "t = 4/s<BR>\n" );
document.write( "---<BR>\n" );
document.write( "downhill time:<BR>\n" );
document.write( "t = 6/(s + 4)<BR>\n" );
document.write( "---<BR>\n" );
document.write( "total time:<BR>\n" );
document.write( "4/s + 6/(s + 4) = 1<BR>\n" );
document.write( "4(s + 4)/s(s + 4) + 6s/s(s + 4) = 1<BR>\n" );
document.write( "4(s + 4) + 6s = s(s + 4)<BR>\n" );
document.write( "4s + 16 + 6s = ss + 4s<BR>\n" );
document.write( "ss - 6s - 16 = 0<BR>\n" );
document.write( "s^2 - 6s - 16 = 0<BR>\n" );
document.write( "---<BR>\n" );
document.write( "the above quadratic equation is in standard form, with a=1, b=-6, and c=-16<BR>\n" );
document.write( "---<BR>\n" );
document.write( "to solve the quadratic equation, plug this:<BR>\n" );
document.write( "1 -6 -16<BR>\n" );
document.write( "into this: https://sooeet.com/math/quadratic-equation-solver.php<BR>\n" );
document.write( "---<BR>\n" );
document.write( "the quadratic roots are:<BR>\n" );
document.write( "---<BR>\n" );
document.write( "s = 8<BR>\n" );
document.write( "s = -2<BR>\n" );
document.write( "---<BR>\n" );
document.write( "the negative root doesn't make sense for speed in this problem, so use the positive root<BR>\n" );
document.write( "---<BR>\n" );
document.write( "speed on flat ground = 8 mph<BR>\n" );
document.write( "speed downhill = 12 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( "Calculate and graph the linear regression of any data set:<BR>\n" );
document.write( "https://sooeet.com/math/linear-regression.php </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );