document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=978713>Question 978713</A>: <I><SPAN STYLE=\"word-break: break-all;\"> you have a lump sum of 80000 to invest. you decided to invest in unit trusts.the unit trust aims to perfom at return of cpi which is about 8%,how long will you have to keep these unit trusts if you want your lump sum to double. </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #600106 by </B><A HREF=/tutors/aboutme.mpl?userid=Theo><B>Theo(13342)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Theo><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=Theo><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=600106\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> f = p * (1+r)^n\r<BR>\n" );
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document.write( "f = future value = 160000<BR>\n" );
document.write( "p = present value = 80000<BR>\n" );
document.write( "note that 160000 = 2 times 80000<BR>\n" );
document.write( "r = 8%/100 = .08<BR>\n" );
document.write( "n = what you want to find.\r<BR>\n" );
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document.write( "your equation is:\r<BR>\n" );
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document.write( "160000 = 80000 * (1.08)^n\r<BR>\n" );
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document.write( "divide both sides of othis equation by 80000 to get:\r<BR>\n" );
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document.write( "2 = 1.08^n\r<BR>\n" );
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document.write( "take the natural log of both sides of the equation to get:\r<BR>\n" );
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document.write( "ln(2) = ln(1.08^n)\r<BR>\n" );
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document.write( "this is equivalent to:\r<BR>\n" );
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document.write( "ln(2) = n*ln(1.08)\r<BR>\n" );
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document.write( "divide both sides of the equation by ln(1.08) to get:\r<BR>\n" );
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document.write( "ln(2) / ln(1.08) = n\r<BR>\n" );
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document.write( "solve for n to get:\r<BR>\n" );
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document.write( "n = 9.006468.\r<BR>\n" );
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document.write( "confirm by replacing n in the original equation with 9.006468.\r<BR>\n" );
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document.write( "160000 = 80000 * (1.08)^9.006468\r<BR>\n" );
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document.write( "solve to get:\r<BR>\n" );
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document.write( "160000 = 160000\r<BR>\n" );
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document.write( "this confirms the solution is correct.\r<BR>\n" );
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document.write( " </SPAN>\n" );
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