document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1034059>Question 1034059</A>: <I><SPAN STYLE=\"word-break: break-all;\"> An airplane climbs 100 feet during the first second after takeoff. In each succeeding second it climbs 100 feet more than it climbed during the previous second. How many seconds does it take for the plane to reach an altitude of<BR>\n" );
document.write( "12,000 feet above its takeoff height?\r<BR>\n" );
document.write( "\n" );
document.write( "Answer 15 seconds (How?) </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #648768 by </B><A HREF=/tutors/aboutme.mpl?userid=fractalier><B>fractalier(6550)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=fractalier><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=fractalier><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=648768\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Well, the situation describes the series<BR>\n" );
document.write( "100 + 200 + 300 + 400 + ...where the total is the overall height of the airplane...we want to know when this total exceeds 12000...<BR>\n" );
document.write( "Such an arithmetic series and sum can be described mathematically as<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=S%5Bn%5D+=+%28n%2F2%29%282a%5B1%5D+%2B+%28n-1%29d%29 ALIGN=MIDDLE  ALT=\"S%5Bn%5D+=+%28n%2F2%29%282a%5B1%5D+%2B+%28n-1%29d%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "Now plug in to get<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=12000+=+%28n%2F2%29%282%2A100+%2B+%28n-1%29%28100%29%29 ALIGN=MIDDLE  ALT=\"12000+=+%28n%2F2%29%282%2A100+%2B+%28n-1%29%28100%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=12000+=+%28n%2F2%29%28200+%2B+100n+-+100%29 ALIGN=MIDDLE  ALT=\"12000+=+%28n%2F2%29%28200+%2B+100n+-+100%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=12000+=+%28n%2F2%29%28100n+%2B+100%29 ALIGN=MIDDLE  ALT=\"12000+=+%28n%2F2%29%28100n+%2B+100%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "Continue solving for n...<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=12000+=+50n%28n+%2B+1%29 ALIGN=MIDDLE  ALT=\"12000+=+50n%28n+%2B+1%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=240+=+n%28n%2B1%29 ALIGN=MIDDLE  ALT=\"240+=+n%28n%2B1%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=n%5E2+%2B+n+-+240+=+0 ALIGN=MIDDLE  ALT=\"n%5E2+%2B+n+-+240+=+0\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%28n%2B16%29%28n-15%29+=+0 ALIGN=MIDDLE  ALT=\"%28n%2B16%29%28n-15%29+=+0\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "n = 15<BR>\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );