document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=994514>Question 994514</A>: <I><SPAN STYLE=\"word-break: break-all;\"> An airplane flies 410 miles with the wind and 310 against the wind in the same length of time.  If the speed of the wind is 40, what is the speed of the airplane in still air?<BR>\n" );
document.write( "A.). 293mph.   B). 288mph.  C). 124mph.  D). 278mph\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "I have tried this:  \r<BR>\n" );
document.write( "\n" );
document.write( "X=d/t.               <BR>\n" );
document.write( "X=410 -40<BR>\n" );
document.write( "X=370\r<BR>\n" );
document.write( "\n" );
document.write( "X=310+40<BR>\n" );
document.write( "X=350<BR>\n" );
document.write( " </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #613562 by </B><A HREF=/tutors/aboutme.mpl?userid=josgarithmetic><B>josgarithmetic(39625)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=josgarithmetic><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/images/nopicture.jpg><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=613562\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Assign some variables.<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=system%28r=unknownPlaneSpeed%2Cw=40WindSpeed%2Cm=410MilesWithWind%2Cn=310MilesAgainstWind%2Ct=unknownSameTimeBothDirections%29 ALIGN=MIDDLE   DISABLED_style= \"max-width:90%; height:auto;\" >\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "Uniform Rates Travel Rule, RT=D to relate rate, time, distance;<BR>\n" );
document.write( "also can be used as R=D/T.\r<BR>\n" );
document.write( "\n" );
document.write( "<PRE STYLE=\"white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;\">\r\n" );
document.write( "Direction   speed        time       distance\r\n" );
document.write( "WITH        r+w           t          m\r\n" );
document.write( "AGAINST     r-w           t          n\r\n" );
document.write( "</PRE><BR>\n" );
document.write( "See that the same number in the same variable t is used for both directions.  The question asks for r, but not for t.<BR>\n" );
document.write( "<PRE STYLE=\"white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;\">\r\n" );
document.write( "Direction   speed        time              distance\r\n" );
document.write( "WITH        r+w           t=m/(r+w)          m\r\n" );
document.write( "AGAINST     r-w           t=n/(r-w)          n\r\n" );
document.write( "</PRE>\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "Equate the two formulas for time t:<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=highlight%28m%2F%28r%2Bw%29=n%2F%28r-w%29%29 ALIGN=MIDDLE  ALT=\"highlight%28m%2F%28r%2Bw%29=n%2F%28r-w%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "This equation uses only one unknown variable, r, which is what the question asks to find.  Solve the equation for r. </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );