document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=380432>Question 380432</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A plane traveled a distance of 800 miles and returned the same distance. If the rate returning is 40 miles per hour faster than the rate going, and if the total flight took 8 hours, how fast did the plane travel on the return trip? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #269993 by </B><A HREF=/tutors/aboutme.mpl?userid=mananth><B>mananth(16946)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=mananth><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=mananth><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=269993\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Distance = 800 miles . speed going = x mph<BR>\n" );
document.write( "distance = 800 miles : speed = x+40 mph.<BR>\n" );
document.write( "...<BR>\n" );
document.write( "time going +time returning=8<BR>\n" );
document.write( "..<BR>\n" );
document.write( "t=d/r<BR>\n" );
document.write( "800/x+800/(x+40 )= 8<BR>\n" );
document.write( "..<BR>\n" );
document.write( "lcd = x(x+40)<BR>\n" );
document.write( "800(x+40)+800x /x(x+40)=8<BR>\n" );
document.write( "800x+32000+800x=8x^2+320x<BR>\n" );
document.write( "8x^2-1600x+320x-32000=0<BR>\n" );
document.write( "8x^2-1280x-32000=0<BR>\n" );
document.write( "/8<BR>\n" );
document.write( "x^2-160x-4000=0<BR>\n" );
document.write( "..<BR>\n" );
document.write( "find the roots x1,x2 using quadratic formula<BR>\n" );
document.write( "discriminant = 41600<BR>\n" );
document.write( "x1=((160+sqrt(41600))/2<BR>\n" );
document.write( "x1= 181.98 = 182 mph <BR>\n" );
document.write( "x2 is negative so reject.<BR>\n" );
document.write( "return trip speed = x+40 = 182 +40 = 222 mph<BR>\n" );
document.write( "...<BR>\n" );
document.write( "m.ananth@hotmail.ca </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );