document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1209369>Question 1209369</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A sum of money doubles itself in 10 years. The number of years it would triple itself is? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #848692 by </B><A HREF=/tutors/aboutme.mpl?userid=greenestamps><B>greenestamps(13200)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=greenestamps><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=greenestamps><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=848692\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> <br><BR>\n" );
document.write( "Let a be the initial amount; let r be the growth factor each year.  Then, since the amount doubles in 10 years,<br><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=a%28r%5E10%29=2a ALIGN=MIDDLE  ALT=\"a%28r%5E10%29=2a\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=r%5E10=2a%2Fa=2 ALIGN=MIDDLE  ALT=\"r%5E10=2a%2Fa=2\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=r=root%2810%2C2%29 ALIGN=MIDDLE  ALT=\"r=root%2810%2C2%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > = 1.07177 to several decimal places.<br><BR>\n" );
document.write( "We want to find the number of years n it takes the amount to triple:<br><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=a%28r%5En%29=3a ALIGN=MIDDLE  ALT=\"a%28r%5En%29=3a\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=r%5En=3 ALIGN=MIDDLE  ALT=\"r%5En=3\"   DISABLED_style= \"max-width:90%; height:auto;\" ><br><BR>\n" );
document.write( "The variable is in an exponent, so use logarithms.<br><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=n%2Alog%28r%29=log%283%29 ALIGN=MIDDLE  ALT=\"n%2Alog%28r%29=log%283%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=n=log%283%29%2Flog%28r%29 ALIGN=MIDDLE  ALT=\"n=log%283%29%2Flog%28r%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > = 15.85 to two decimal places<br><BR>\n" );
document.write( "ANSWER: approximately 15.85 years<br><BR>\n" );
document.write( "Of course, if we want an answer in whole numbers of years we need to round that up to 16 years.<br><BR>\n" );
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