document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=443549>Question 443549</A>: <I><SPAN STYLE=\"word-break: break-all;\"> What is the last number in this sum?<BR>\n" );
document.write( "1 + 3 + 5 + ... + ? = 10,000 </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #305940 by </B><A HREF=/tutors/aboutme.mpl?userid=edjones><B>edjones(8007)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=edjones><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=edjones><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=305940\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Let n=number of terms in the sum.<BR>\n" );
document.write( "The first term (a[1]) is 1.<BR>\n" );
document.write( "The last term (a[n]) must be 2n-1.<BR>\n" );
document.write( "n/2(a[1]+a[n])=S Formula for the sum of an finite arithmetic sequence.<BR>\n" );
document.write( "n/2(1+(2n-1))=10000<BR>\n" );
document.write( "n(1+2n-1)=20000<BR>\n" );
document.write( "n+2n^2-n=20000<BR>\n" );
document.write( "2n^2=20000<BR>\n" );
document.write( "n^2=10000<BR>\n" );
document.write( "n=100<BR>\n" );
document.write( "a[100]=2*100-1=199<BR>\n" );
document.write( ".<BR>\n" );
document.write( "Ed </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );