document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=992214>Question 992214</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A jet plane, flying 80 mph faster than a propeller plane, travels 3960 miles in 2 hours less time than the propeller plane takes to fly the same distance. How fast does each plane fly? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #611853 by </B><A HREF=/tutors/aboutme.mpl?userid=ankor@dixie-net.com><B>ankor@dixie-net.com(22740)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=ankor@dixie-net.com><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=ankor@dixie-net.com><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=611853\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\">  A jet plane, flying 80 mph faster than a propeller plane, travels 3960 miles in 2 hours less time than the propeller plane takes to fly the same distance.<BR>\n" );
document.write( " How fast does each plane fly?<BR>\n" );
document.write( ":<BR>\n" );
document.write( "let s = the speed of the prop plane<BR>\n" );
document.write( "then<BR>\n" );
document.write( "(s+80) = speed of the jet<BR>\n" );
document.write( ":<BR>\n" );
document.write( "Write a time equation; time = dist/speed<BR>\n" );
document.write( "Prop time - jet time = 2 hrs<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=3960%2Fs ALIGN=MIDDLE  ALT=\"3960%2Fs\"   DISABLED_style= \"max-width:90%; height:auto;\" > - <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=3960%2F%28%28s%2B80%29%29 ALIGN=MIDDLE  ALT=\"3960%2F%28%28s%2B80%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > = 2<BR>\n" );
document.write( "multiply the equation by s(s+80)<BR>\n" );
document.write( "s(s+80)*<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=3960%2Fs ALIGN=MIDDLE  ALT=\"3960%2Fs\"   DISABLED_style= \"max-width:90%; height:auto;\" > - s(s+80)*<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=3960%2F%28%28s%2B80%29%29 ALIGN=MIDDLE  ALT=\"3960%2F%28%28s%2B80%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > = 2s(s+80)<BR>\n" );
document.write( "cancel the denominators and you have<BR>\n" );
document.write( "3960(s+80) - 3960s = 2s^2 + 160s<BR>\n" );
document.write( "3960s + 316800 - 3960s = 2s^2 + 160s<BR>\n" );
document.write( "combine to form a quadratic equation<BR>\n" );
document.write( "0 = 2s^2 + 160s - 316800 <BR>\n" );
document.write( "simplify divide by 2<BR>\n" );
document.write( "s^2 + 80s - 158400 = 0<BR>\n" );
document.write( "you can use the quadratic formula to find s a=1; b=80; c=158400<BR>\n" );
document.write( "but this will factor<BR>\n" );
document.write( "(s+440)(s-360) = 0<BR>\n" );
document.write( "the positive solution<BR>\n" );
document.write( "s = 360 mph is the speed of the prop plane<BR>\n" );
document.write( "the jet 80 mph faster, hence<BR>\n" );
document.write( "440 mph is speed of the jet<BR>\n" );
document.write( ":<BR>\n" );
document.write( ":<BR>\n" );
document.write( "Check this by finding the actual time of each plane<BR>\n" );
document.write( "3960/360 = 11 hrs for prop to make the trip<BR>\n" );
document.write( "3960/440 =  9 hrs for the jet </SPAN>\n" );
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