document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=407183>Question 407183</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A train can hold 78 passengers. The train starts out empty and picks up one passenger at the first stop,2 passengers at the second stop,3 passengers at the third stop,and so forth. After how many stops  will the train be full. </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #287070 by </B><A HREF=/tutors/aboutme.mpl?userid=robertb><B>robertb(5830)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=robertb><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=robertb><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=287070\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Let s = the stop number where the train fills.\r<BR>\n" );
document.write( "\n" );
document.write( "Then 1+2+3+...+s = 78, or\r<BR>\n" );
document.write( "\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%28s%28s%2B1%29%29%2F2+=+78 ALIGN=MIDDLE  ALT=\"%28s%28s%2B1%29%29%2F2+=+78\"   DISABLED_style= \"max-width:90%; height:auto;\" >, or<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=s%5E2+%2B+s+=+156 ALIGN=MIDDLE  ALT=\"s%5E2+%2B+s+=+156\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=s%5E2+%2B+s+-+156+=+0 ALIGN=MIDDLE  ALT=\"s%5E2+%2B+s+-+156+=+0\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(s+13)(s-12) = 0<BR>\n" );
document.write( "==> s = 12.\r<BR>\n" );
document.write( "\n" );
document.write( "Hence on the 12th stop the train is full. </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );