document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1003374>Question 1003374</A>: <I><SPAN STYLE=\"word-break: break-all;\"> an arithmetic progression has the 8th term being twice the 4th term. if the 20th term is 40, find the sum of the first 20 terms of the series. </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #620100 by </B><A HREF=/tutors/aboutme.mpl?userid=mananth><B>mananth(16946)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=mananth><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=mananth><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=620100\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> nth. term of an AP is a+(n-1) d\r<BR>\n" );
document.write( "\n" );
document.write( "a8 = a+7d<BR>\n" );
document.write( "a4 = a+3d\r<BR>\n" );
document.write( "\n" );
document.write( "2(a+3d) = a+7d\r<BR>\n" );
document.write( "\n" );
document.write( "2a+6d = a+7d\r<BR>\n" );
document.write( "\n" );
document.write( "a=d\r<BR>\n" );
document.write( "\n" );
document.write( "a20 = a+19d\r<BR>\n" );
document.write( "\n" );
document.write( "40 = a+19a\r<BR>\n" );
document.write( "\n" );
document.write( "20a=40<BR>\n" );
document.write( "a= 2<BR>\n" );
document.write( "d=2\r<BR>\n" );
document.write( "\n" );
document.write( "Sn = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%28n%2F2%29%282a%2B%28n-1%29d%29 ALIGN=MIDDLE  ALT=\"%28n%2F2%29%282a%2B%28n-1%29d%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >\r<BR>\n" );
document.write( "\n" );
document.write( "S20 = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%2820%2F2%29%2A%282%2A2%2B19%2A2%29 ALIGN=MIDDLE  ALT=\"%2820%2F2%29%2A%282%2A2%2B19%2A2%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >\r<BR>\n" );
document.write( "\n" );
document.write( "= 10(4+38)<BR>\n" );
document.write( "10*42<BR>\n" );
document.write( "=420\r<BR>\n" );
document.write( "\n" );
document.write( "S20 = 420\r<BR>\n" );
document.write( "\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );