document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=821894>Question 821894</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A pilot found that it took 3/4 as long to travel 100 kilometers with a 30 km/hr tailwind as it took to travel the same distance with a 30 km/hr headwind. Find the  speed of the plane in still air. </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #494492 by </B><A HREF=/tutors/aboutme.mpl?userid=ankor@dixie-net.com><B>ankor@dixie-net.com(22740)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=ankor@dixie-net.com><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=ankor@dixie-net.com><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=494492\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> A pilot found that it took 3/4 as long to travel 100 kilometers with a 30 km/hr tailwind as it took to travel the same distance with a 30 km/hr headwind.<BR>\n" );
document.write( " Find the speed of the plane in still air.<BR>\n" );
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document.write( "Let s = speed of plane in still air<BR>\n" );
document.write( "then<BR>\n" );
document.write( "(s+30) = effective ground speed with the wind<BR>\n" );
document.write( "and<BR>\n" );
document.write( "(s-30) = effective ground speed against the wind<BR>\n" );
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document.write( "let d = the one way distance (we don't need to know the distance)<BR>\n" );
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document.write( "Write a time equation, time = dist/speed<BR>\n" );
document.write( "use the decimal equiv of 3/4<BR>\n" );
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document.write( "with wind time = 3/4 against wind time<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=d%2F%28%28s%2B30%29%29 ALIGN=MIDDLE  ALT=\"d%2F%28%28s%2B30%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > = .75(<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=d%2F%28%28s-30%29%29 ALIGN=MIDDLE  ALT=\"d%2F%28%28s-30%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >)<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=d%2F%28%28s%2B30%29%29 ALIGN=MIDDLE  ALT=\"d%2F%28%28s%2B30%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%28.75d%29%2F%28%28s-30%29%29 ALIGN=MIDDLE  ALT=\"%28.75d%29%2F%28%28s-30%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "Cross multiply<BR>\n" );
document.write( "d(s-30) = .75d(s+30)<BR>\n" );
document.write( "divide both sides by d<BR>\n" );
document.write( "s-30 = .75(s+30)<BR>\n" );
document.write( "s - 30 = .75s + 22.5<BR>\n" );
document.write( "s - .75s = 22.5 + 30<BR>\n" );
document.write( ".25s = 52.5<BR>\n" );
document.write( "s = 52.5/.25<BR>\n" );
document.write( "s = 210 km/h plane speed in still air<BR>\n" );
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document.write( "You can check this using a distance of 100 km<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=100%2F240 ALIGN=MIDDLE  ALT=\"100%2F240\"   DISABLED_style= \"max-width:90%; height:auto;\" > = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=3%2F4 ALIGN=MIDDLE  ALT=\"3%2F4\"   DISABLED_style= \"max-width:90%; height:auto;\" >*<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=100%2F180%29 ALIGN=MIDDLE  ALT=\"100%2F180%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );