document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=825285>Question 825285</A>: <I><SPAN STYLE=\"word-break: break-all;\"> an airplane makes a 990 km flight with a tailwind and returns, flying into the same wind. The total flying time is 3 hours 20 minutes, and the airplane's speed in still air is 600 km/h. What is the speed of the wind? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #497198 by </B><A HREF=/tutors/aboutme.mpl?userid=josmiceli><B>josmiceli(19441)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=josmiceli><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=josmiceli><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=497198\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Let <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+w+ ALIGN=MIDDLE  ALT=\"+w+\"   DISABLED_style= \"max-width:90%; height:auto;\" > = the speed of the wind<BR>\n" );
document.write( "Flying with the wind<BR>\n" );
document.write( "Let <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+t+ ALIGN=MIDDLE  ALT=\"+t+\"   DISABLED_style= \"max-width:90%; height:auto;\" > = the flying time flying with the wind<BR>\n" );
document.write( "----------------------------------------<BR>\n" );
document.write( "with the wind<BR>\n" );
document.write( "(1) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+990+=+%28+600+%2B+w+%29%2At+ ALIGN=MIDDLE  ALT=\"+990+=+%28+600+%2B+w+%29%2At+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "against the wind<BR>\n" );
document.write( "(2) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+990+=+%28+600+-+w+%29%2A%28+10%2F3+-+t+%29+ ALIGN=MIDDLE  ALT=\"+990+=+%28+600+-+w+%29%2A%28+10%2F3+-+t+%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "---------------------------------<BR>\n" );
document.write( "(1) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+t+=+990+%2F+%28+600+%2B+w+%29+ ALIGN=MIDDLE  ALT=\"+t+=+990+%2F+%28+600+%2B+w+%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(2) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+990+=+2000+-+%2810%2F3%29%2Aw+-+600t+%2B+w%2At+ ALIGN=MIDDLE  ALT=\"+990+=+2000+-+%2810%2F3%29%2Aw+-+600t+%2B+w%2At+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "---------------------------------------<BR>\n" );
document.write( "Substitute (1) into (2)<BR>\n" );
document.write( "(2) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+990+=+2000+-+%2810%2F3%29%2Aw+-+%28+600+-+w+%29%2A%28+990%2F%28+600+%2B+w+%29%29+ ALIGN=MIDDLE  ALT=\"+990+=+2000+-+%2810%2F3%29%2Aw+-+%28+600+-+w+%29%2A%28+990%2F%28+600+%2B+w+%29%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(2) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+-1010+=+-+%2810%2F3%29%2Aw+-+%28+600+-+w+%29%2A%28+990%2F%28+600+%2B+w+%29%29+ ALIGN=MIDDLE  ALT=\"+-1010+=+-+%2810%2F3%29%2Aw+-+%28+600+-+w+%29%2A%28+990%2F%28+600+%2B+w+%29%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(2) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+1010+=++%2810%2F3%29%2Aw+%2B+%28+600+-+w+%29%2A%28+990%2F%28+600+%2B+w+%29%29+ ALIGN=MIDDLE  ALT=\"+1010+=++%2810%2F3%29%2Aw+%2B+%28+600+-+w+%29%2A%28+990%2F%28+600+%2B+w+%29%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "Multiply both sides by <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+3%2A%28+600+%2B+w+%29+ ALIGN=MIDDLE  ALT=\"+3%2A%28+600+%2B+w+%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(2) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+3030%2A%28+600+%2B+w+%29+=+10w%2A%28+600+%2B+w+%29+%2B+3%2A990%2A%28+600+-+w+%29+ ALIGN=MIDDLE  ALT=\"+3030%2A%28+600+%2B+w+%29+=+10w%2A%28+600+%2B+w+%29+%2B+3%2A990%2A%28+600+-+w+%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(2) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+1818000+%2B+3030w++=+6000w+%2B+10w%5E2+%2B+1782000+-+2970w++ ALIGN=MIDDLE  ALT=\"+1818000+%2B+3030w++=+6000w+%2B+10w%5E2+%2B+1782000+-+2970w++\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(2) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+10w%5E2+-+3030w+%2B+6000w+-+2970w+%2B+1782000+-+1818000+=+0+ ALIGN=MIDDLE  ALT=\"+10w%5E2+-+3030w+%2B+6000w+-+2970w+%2B+1782000+-+1818000+=+0+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(2) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+10w%5E2+-+36000+=+0+ ALIGN=MIDDLE  ALT=\"+10w%5E2+-+36000+=+0+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(2) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+10w%5E2+=+36000+ ALIGN=MIDDLE  ALT=\"+10w%5E2+=+36000+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(2) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+w%5E2+=+3600+ ALIGN=MIDDLE  ALT=\"+w%5E2+=+3600+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(2) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+w+=+60+ ALIGN=MIDDLE  ALT=\"+w+=+60+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "The wind speed is 60 km/hr<BR>\n" );
document.write( "------------------------<BR>\n" );
document.write( "check:<BR>\n" );
document.write( "(1) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+990+=+%28+600+%2B+60+%29%2At+ ALIGN=MIDDLE  ALT=\"+990+=+%28+600+%2B+60+%29%2At+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(1) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+t+=+990+%2F+660+ ALIGN=MIDDLE  ALT=\"+t+=+990+%2F+660+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(1) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+t+=+1.5+ ALIGN=MIDDLE  ALT=\"+t+=+1.5+\"   DISABLED_style= \"max-width:90%; height:auto;\" > hrs<BR>\n" );
document.write( "and<BR>\n" );
document.write( "(2) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+990+=+%28+600+-+60+%29%2A%28+10%2F3+-+t+%29+ ALIGN=MIDDLE  ALT=\"+990+=+%28+600+-+60+%29%2A%28+10%2F3+-+t+%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(2) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+990+=+540%2A%28+10%2F3+-+t+%29+ ALIGN=MIDDLE  ALT=\"+990+=+540%2A%28+10%2F3+-+t+%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(2) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+990+=+1800+-+540t+ ALIGN=MIDDLE  ALT=\"+990+=+1800+-+540t+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(2) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+540t+=+1800+-+990+ ALIGN=MIDDLE  ALT=\"+540t+=+1800+-+990+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(2) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+540t+=+810+ ALIGN=MIDDLE  ALT=\"+540t+=+810+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(2) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+t+=+1.5+ ALIGN=MIDDLE  ALT=\"+t+=+1.5+\"   DISABLED_style= \"max-width:90%; height:auto;\" > hrs<BR>\n" );
document.write( "OK<BR>\n" );
document.write( " \r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );