document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=745077>Question 745077</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Please help If the number of terms of an Arithmetic sequence is 15 and the value of it's middle term is 10 then find the sum of it's terms is there any rule that i can solve it with?? Thanks </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #453702 by </B><A HREF=/tutors/aboutme.mpl?userid=sachi><B>sachi(548)</B></A><img src=\"/images/stars/stars-10.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=sachi><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=sachi><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=453702\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> the number of terms of an Arithmetic sequence is 15 <BR>\n" );
document.write( "so the middle term= (15+1)/2=8th term (+1 for odd no of terms)<BR>\n" );
document.write( "so t8=a+(8-1)d=a+7d  (a,d being 1st term & common difference)<BR>\n" );
document.write( "the value of it's middle term is 10 <BR>\n" );
document.write( "so a+7d=10.........1<BR>\n" );
document.write( "the sum of it's terms is S15=(15/2)*(2a+[15-1]d)=7.5*(2a+14d)=7.5*2*(a+7d)<BR>\n" );
document.write( "=7.5*2*10=150  putting the value from eqn 1\r<BR>\n" );
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document.write( "so the sum =150 </SPAN>\n" );
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