document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=64140>Question 64140</A>This question is from textbook <A HREF=http://www.amazon.com/exec/obidos/ASIN/0072549017/algebrahomeworkh>Beginning Algebra</A><BR>\n" );
document.write( ": <I><SPAN STYLE=\"word-break: break-all;\"> A plane flies 720 miles against a steady headwind and then returns to the same point with the wind. If the entire trip takes 10 hours what is the planes speed in  still air? \r<BR>\n" );
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document.write( "I have attempted to solve this by using the formula: <BR>\n" );
document.write( "720/(x+30)=720/(x-30) and needless to say do not get the correct answer. The 10 hours is throwing me off. I think the answer is 144mph but cannot get the formula to produce the result. What am I missing? Thanks.  </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #44798 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=44798\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> The plane travels 2*720 mi or 1440 mi in 10 hours <BR>\n" );
document.write( "d / t = r , so 1440 / 10 = 144 m i/hr is the planes <BR>\n" );
document.write( "speed in still air.<BR>\n" );
document.write( "Whatever the windspeed is, it's effect in one direction <BR>\n" );
document.write( "will cancel it's effect in the opposite direction <BR>\n" );
document.write( "because the plane goes the same distance with<BR>\n" );
document.write( "and against the wind. <BR>\n" );
document.write( "Actually, I believe this problem, as stated, is physically<BR>\n" );
document.write( "impossible. The plane can't reverse direction without<BR>\n" );
document.write( "slowing down and maintain it's speed in the opposite di-<BR>\n" );
document.write( "rection.<BR>\n" );
document.write( "Even if you change the problem and say that the plane keeps<BR>\n" );
document.write( "going in the same direction for 1440 mi and it is only the<BR>\n" );
document.write( "windspeed that reverses diretion at the halfway point,<BR>\n" );
document.write( "any value that you select for the windspeed (other than 0)<BR>\n" );
document.write( "will make the planes speed in still air turn out to be<BR>\n" );
document.write( "greater than 144 mi/hr.<BR>\n" );
document.write( "w = windspeed<BR>\n" );
document.write( "p =planes speed instill air<BR>\n" );
document.write( "The equation I end up with is<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=p%5E2+-144p+-w%5E2+=+0 ALIGN=MIDDLE  ALT=\"p%5E2+-144p+-w%5E2+=+0\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "that's using<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=720%2F%28w%2Bp%29+%2B+720%2F%28-w%2Bp%29+=+10 ALIGN=MIDDLE  ALT=\"720%2F%28w%2Bp%29+%2B+720%2F%28-w%2Bp%29+=+10\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "The only way you can get p = 144 is if w = 0<BR>\n" );
document.write( "If I say w = 18 mi/hr, I get p = 146.21 mi/hr<BR>\n" );
document.write( "If I say w = 9 mi/hr, I get p = 144.5 mi/hr<BR>\n" );
document.write( "There is a simple answer to this, but you just couldn't <BR>\n" );
document.write( "do it in real life. A lot of problems are like that<BR>\n" );
document.write( "and my answer is- if a simple answer is what they <BR>\n" );
document.write( "want, give it to them, but watch out for the<BR>\n" );
document.write( "\"trick\" questions when they want you to think a lot.<BR>\n" );
document.write( "I could be all wrong about this, but I don't think so.   </SPAN>\n" );
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