document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=967397>Question 967397</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A sum of $1200 is invested at an interest rate of 4.5 % compounded annually. How many years will it take until the sum exceeds $2100?  </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #591261 by </B><A HREF=/tutors/aboutme.mpl?userid=jim_thompson5910><B>jim_thompson5910(35256)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=jim_thompson5910><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=591261\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Plug in the given values and use logs to isolate t.\r<BR>\n" );
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document.write( "A = P*(1+r/n)^(n*t)<BR>\n" );
document.write( "2100 = 1200*(1+0.045/1)^(1*t)<BR>\n" );
document.write( "2100 = 1200*(1+0.045)^t<BR>\n" );
document.write( "2100 = 1200*(1.045)^t<BR>\n" );
document.write( "2100/1200 = 1.045^t<BR>\n" );
document.write( "1.75 = 1.045^t<BR>\n" );
document.write( "1.045^t = 1.75<BR>\n" );
document.write( "log(1.045^t) = log(1.75)<BR>\n" );
document.write( "t*log(1.045) = log(1.75)<BR>\n" );
document.write( "t = log(1.75)/log(1.045)<BR>\n" );
document.write( "t = 12.71366 (this is approximate)\r<BR>\n" );
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document.write( "It will take approximately 12.71366 years for the account to have $2100. Round up to the nearest year, 13 years, and you're guaranteed to have more than $2100 in the account. </SPAN>\n" );
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