document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1054967>Question 1054967</A>: <I><SPAN STYLE=\"word-break: break-all;\"> An investment pays simple interest, and quadruples in 13 years. What is the interest rate?  </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #670196 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=670196\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> the formula for simple interest is i * p * n.\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "i is the interest rate per time period.<BR>\n" );
document.write( "p is the principal.<BR>\n" );
document.write( "n is the number of time periods.\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "the formula for future value of an investment using simple interest is f = p + p * i * n).\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "this can be simplified to f = p * (1 + i * n).\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "you are given that n = 13 years.<BR>\n" );
document.write( "you will be looking for the interest rate per year.<BR>\n" );
document.write( "since you will be quadrupling your money, than f will be equal to 4p.\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "your formula of f = p * (1 + i * n) becomes:\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "4p = p * (1 + 13 * i)\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "divide both sides of this equation by p to get:\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "4 = 1 + 13 * i\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "subtract 1 from both sides of this equation to get:\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "3 = 13 * i\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "divide both sides of this equation by 13 to get:\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "3/13 = i\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "that's your interest rate per year.\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "i = 3/13 = .2307692308\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "for example:\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "assume your principal is equal to 500 dollars.\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "your interest in 13 years will be equal to 500 * 3/13 * 13 which will become 500 * 3 which will become 1500 dollars.\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "add that to your principal of 500 dollars and you get a total of 2000 dollars which is equal to 4 times the original investment of 500 dollars.\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );