document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=937771>Question 937771</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A helicopter flew 15 miles against a 25 mph headwind.  Then it flew back with the wind at its tail.  The round trip lasted 27 minutes.  Find the helicopter's speed in still air.<BR>\n" );
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document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #571196 by </B><A HREF=/tutors/aboutme.mpl?userid=TimothyLamb><B>TimothyLamb(4379)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=TimothyLamb><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=TimothyLamb><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=571196\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> x = time with headwind<BR>\n" );
document.write( "y = time with tailwind<BR>\n" );
document.write( "z = helicopter speed in still air<BR>\n" );
document.write( "---<BR>\n" );
document.write( "s = d/t<BR>\n" );
document.write( "---<BR>\n" );
document.write( "speed in headwind:<BR>\n" );
document.write( "z - 25 = 15/x<BR>\n" );
document.write( "z = 15/x + 25<BR>\n" );
document.write( "---<BR>\n" );
document.write( "speed in tailwind:<BR>\n" );
document.write( "z + 25 = 15/y<BR>\n" );
document.write( "z = 15/y - 25<BR>\n" );
document.write( "---<BR>\n" );
document.write( "equate z's:<BR>\n" );
document.write( "15/x + 25 = 15/y - 25<BR>\n" );
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document.write( "total time:<BR>\n" );
document.write( "x + y = 27/60<BR>\n" );
document.write( "y = 27/60 - x<BR>\n" );
document.write( "---<BR>\n" );
document.write( "15/x + 25 = 15/y - 25<BR>\n" );
document.write( "15/x - 15/y = -50<BR>\n" );
document.write( "y(15/x - 15/y = -50)<BR>\n" );
document.write( "15y/x - 15 = -50y<BR>\n" );
document.write( "15(27/60 - x)/x - 15 = -50(27/60 - x)<BR>\n" );
document.write( "(15*27/60)/x - 15 - 15 = -50*27/60 + 50x<BR>\n" );
document.write( "(15*27/60)/x = -50*27/60 + 30 + 50x<BR>\n" );
document.write( "6.75/x = 7.5 + 50x<BR>\n" );
document.write( "50x - 6.75/x + 7.5 = 0<BR>\n" );
document.write( "50xx + 7.5x - 6.75 = 0<BR>\n" );
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document.write( "the above quadratic equation is in standard form, with a=50, b=7.5 and c=-6.75<BR>\n" );
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document.write( "to solve the quadratic equation, by using the quadratic formula, copy and paste this:<BR>\n" );
document.write( "50 7.5 -6.75<BR>\n" );
document.write( "into this solver: https://sooeet.com/math/quadratic-equation-solver.php<BR>\n" );
document.write( "---<BR>\n" );
document.write( "the quadratic has two real roots at:<BR>\n" );
document.write( "---<BR>\n" );
document.write( "x = 0.3<BR>\n" );
document.write( "x = -0.45<BR>\n" );
document.write( "---<BR>\n" );
document.write( "the negative root doesn't fit the problem statement, so use the positive root:<BR>\n" );
document.write( "---<BR>\n" );
document.write( "x = 0.3 hr<BR>\n" );
document.write( "y = 27/60 - x<BR>\n" );
document.write( "y = 27/60 - 0.3<BR>\n" );
document.write( "y = 0.15 hr<BR>\n" );
document.write( "---<BR>\n" );
document.write( "answer:<BR>\n" );
document.write( "z = 15/x + 25<BR>\n" );
document.write( "z = 15/0.3 + 25<BR>\n" );
document.write( "z = helicopter speed in still air = 75 mph<BR>\n" );
document.write( "---<BR>\n" );
document.write( "Free algebra tutoring live chat:<BR>\n" );
document.write( "https://sooeet.com/chat.php?gn=algebra<BR>\n" );
document.write( "---<BR>\n" );
document.write( "Solve and graph linear equations:<BR>\n" );
document.write( "https://sooeet.com/math/linear-equation-solver.php<BR>\n" );
document.write( "---<BR>\n" );
document.write( "Solve quadratic equations with quadratic formula:<BR>\n" );
document.write( "https://sooeet.com/math/quadratic-formula-solver.php<BR>\n" );
document.write( "---<BR>\n" );
document.write( "Solve systems of linear equations up to 6-equations 6-variables:<BR>\n" );
document.write( "https://sooeet.com/math/system-of-linear-equations-solver.php<BR>\n" );
document.write( "--- </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );