document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=539555>Question 539555</A>: <I><SPAN STYLE=\"word-break: break-all;\"> a plane left an airport and flew with the wind for 4 hours, covering 2,000 kilometers. it then returned over the same route against the same wind in 5 hours. find the rate of the plane in still air and 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 #353460 by </B><A HREF=/tutors/aboutme.mpl?userid=oberobic><B>oberobic(2304)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=oberobic><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=353460\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> a = airspeed of the plane in calm air<BR>\n" );
document.write( "w = wind speed<BR>\n" );
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document.write( "ground speed with a tailwind = a+w<BR>\n" );
document.write( "ground speed with a headwind = a-w<BR>\n" );
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document.write( "d = 2000 km<BR>\n" );
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document.write( "(a+w) *4 hr = 2000 km<BR>\n" );
document.write( "a+w = 500 km/hr<BR>\n" );
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document.write( "(a-w) *5 hr = 2000 km<BR>\n" );
document.write( "a-w = 400 km/hr<BR>\n" );
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document.write( "a + w = 500<BR>\n" );
document.write( "a - w = 400<BR>\n" );
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document.write( "2a = 900<BR>\n" );
document.write( "a = 450<BR>\n" );
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document.write( "a+w = 500<BR>\n" );
document.write( "w = 50<BR>\n" );
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document.write( "Check the distances traveled over the given times.<BR>\n" );
document.write( "(450+50) km/hr * 4 hr = 2000 km<BR>\n" );
document.write( "(450-50) km/hr * 5 hr = 2000 km<BR>\n" );
document.write( "Correct<BR>\n" );
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document.write( "Answer:  The rate of the plane in calm air is 450 km/hr. The wind speed is 50 km/hr.<BR>\n" );
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document.write( "Done. </SPAN>\n" );
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