document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=184155>Question 184155</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A jet, traveling at an average speed of 420 miles per hour in still air, flew 240 miles and back in 1 hour and 10 minutes. What is the average speed of the wind in mph?  </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #138220 by </B><A HREF=/tutors/aboutme.mpl?userid=ptaylor><B>ptaylor(2198)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=ptaylor><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=ptaylor><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=138220\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> <BR>\n" );
document.write( "Distance(d) equals Rate(r) times Time(t) or d=rt;  r=d/t and t=d/r\r<BR>\n" );
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document.write( "Let s=speed of the wind<BR>\n" );
document.write( "With the wind, add wind speed; against the wind subtract<BR>\n" );
document.write( "Time travelling with the wind= 240/(420+s)<BR>\n" );
document.write( "Time travelling against the wind=240/(420-s)<BR>\n" );
document.write( "Now we are told that the above two times add up to 1 hr 10min=1 1/6=7/6 hr so:<BR>\n" );
document.write( "240/(420+s) +240/(420-s)=7/6  multiply each term by 6(420+s)(420-s)<BR>\n" );
document.write( "1440(420-s)+1440(420+s)=7(420+s)(420-s) get rid of parens<BR>\n" );
document.write( "1440*420-1440s+1440*420+1440s=7*176400-7s^2<BR>\n" );
document.write( "YOU KNOW, THERE MAY BE AN EASIER WAY BUT THE ONLY THING I CAN SEE TO DO RIGHT NOW IS GRIND OUT THE BIG NUMBERS.\r<BR>\n" );
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document.write( "604800+604800=1234800-7s^2 this equals<BR>\n" );
document.write( "1209600=1234800-7s^2 subtract 1234800 from each side<BR>\n" );
document.write( "-7s^2=-25200 divide each side by -7<BR>\n" );
document.write( "s^2=3600   take square root of each side<BR>\n" );
document.write( "s=+or- 60 mph-------------------------------------------------speed of the wind<BR>\n" );
document.write( "disregard the negative value for s; wind speed is positive\r<BR>\n" );
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document.write( "CK<BR>\n" );
document.write( "240/(420+60) +240/(420-60)=7/6<BR>\n" );
document.write( "240/480 + 240/360=7/6<BR>\n" );
document.write( "1/2 + 2/3=7/6<BR>\n" );
document.write( "3/6+ 4/6=7/6<BR>\n" );
document.write( "7/6=7/6\r<BR>\n" );
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document.write( "Hope this helps---ptaylor\r<BR>\n" );
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document.write( " </SPAN>\n" );
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