document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=455271>Question 455271</A>: <I><SPAN STYLE=\"word-break: break-all;\"> I need help with this problem:\r<BR>\n" );
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document.write( "Specify the range of f(x)=x -[x], where [x] is the greatest-interger function. Use the compound interest formula to prove the rule of 70: investment doubling time 70 where r is the nominal interest rate expressed as a percentage (number between zero and 100).\r<BR>\n" );
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document.write( "Thank you! </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #312576 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=312576\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> I need help with this problem: <BR>\n" );
document.write( "Specify the range of f(x)=x -[x], where [x] is the greatest-integer function.<BR>\n" );
document.write( "---<BR>\n" );
document.write( "Graph y = x<BR>\n" );
document.write( "Graph y = [[x]]<BR>\n" );
document.write( "Range = [0,1)<BR>\n" );
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document.write( "Use the compound interest formula to prove the rule of 70: investment doubling time 70 where r is the nominal interest rate expressed as a percentage (number between zero and 100).<BR>\n" );
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document.write( "Let P be the pricipal.<BR>\n" );
document.write( "Doubling  2P = Pe^(rt)<BR>\n" );
document.write( "e^(rt) = 2<BR>\n" );
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document.write( "Take the natural log to get<BR>\n" );
document.write( "rt = ln2<BR>\n" );
document.write( "t = (0.69)/r<BR>\n" );
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document.write( "time = 69/(interest rate expressed as a whole number)<BR>\n" );
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document.write( "Example: <BR>\n" );
document.write( "at 8% doubling time = 69/8 = 8.65 years <BR>\n" );
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document.write( "Cheers,<BR>\n" );
document.write( "Stan H. </SPAN>\n" );
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