document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=140835>Question 140835</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Can someone help me calculate the 20th partial sum for 6400,1600,400,100,25...? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #102478 by </B><A HREF=/tutors/aboutme.mpl?userid=stanbon><B>stanbon(75887)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=stanbon><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/images/nopicture.jpg><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=102478\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> calculate the 20th partial sum for 6400,1600,400,100,25...?<BR>\n" );
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document.write( "You have a geometric sequence with r = (1/4), and a(1)=6400.<BR>\n" );
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document.write( "S(20) = 6400[r^n -1]/[r-1]<BR>\n" );
document.write( "S(20) = 6400[(1/4)^20 -1]/[-3/4]<BR>\n" );
document.write( "S(20) = 8533.3333...<BR>\n" );
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document.write( "Cheers,<BR>\n" );
document.write( "Stan H.<BR>\n" );
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