document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=181467>Question 181467</A>: <I><SPAN STYLE=\"word-break: break-all;\"> the level of thorium in a sample decreases by a factor of one-half every 2 million years.  A meteorite is discovered to have only 8.6% of its original thorium remaining.  How old is the meteorite?<BR>\n" );
document.write( "I am having a terrible time trying to figure out this question and I need to show my work.  Can you please help me, Heather </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #136083 by </B><A HREF=/tutors/aboutme.mpl?userid=ankor@dixie-net.com><B>ankor@dixie-net.com(22740)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=ankor@dixie-net.com><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=ankor@dixie-net.com><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=136083\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> the level of thorium in a sample decreases by a factor of one-half every 2 million years. A meteorite is discovered to have only 8.6% of its original thorium remaining. How old is the meteorite?<BR>\n" );
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document.write( "The half-life formula: A = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=Ao%2A%282%5E%28-t%2Fh%29%29 ALIGN=MIDDLE  ALT=\"Ao%2A%282%5E%28-t%2Fh%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "Where<BR>\n" );
document.write( "A = final amt<BR>\n" );
document.write( "Ao = initial amt<BR>\n" );
document.write( "t = time years<BR>\n" );
document.write( "h = half-life<BR>\n" );
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document.write( "In this problem, we assume the initial amt is 1 and final amt .086 (8.6%),<BR>\n" );
document.write( "time and half-life in millions of years.<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=Ao%2A%282%5E%28-t%2Fh%29%29 ALIGN=MIDDLE  ALT=\"Ao%2A%282%5E%28-t%2Fh%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > = A<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=1%2A%282%5E%28-t%2F2%29%29 ALIGN=MIDDLE  ALT=\"1%2A%282%5E%28-t%2F2%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > = .086<BR>\n" );
document.write( "we can ignore the 1<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%282%5E%28-t%2F2%29%29 ALIGN=MIDDLE  ALT=\"%282%5E%28-t%2F2%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > = .086<BR>\n" );
document.write( "using logs here<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=log%282%5E%28-t%2F2%29%29 ALIGN=MIDDLE  ALT=\"log%282%5E%28-t%2F2%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > = log(.086)<BR>\n" );
document.write( "log equiv of exponents<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%28-t%2F2%29 ALIGN=MIDDLE  ALT=\"%28-t%2F2%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >*log(2) = log(.086)<BR>\n" );
document.write( "Find the logs<BR>\n" );
document.write( ".301*<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=-t%2F2 ALIGN=MIDDLE  ALT=\"-t%2F2\"   DISABLED_style= \"max-width:90%; height:auto;\" > = -1.0655<BR>\n" );
document.write( "Multiply both sides by 2<BR>\n" );
document.write( "-.301t = -2.131<BR>\n" );
document.write( "t = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%28-2.131%29%2F%28-.301%29 ALIGN=MIDDLE  ALT=\"%28-2.131%29%2F%28-.301%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "t = 7.08 million years to decay to 8.6%<BR>\n" );
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document.write( "Check on a calc: enter: 2^(-7.08/2) = .086 ~ 8.6%\r<BR>\n" );
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document.write( "did this help you? any questions\r<BR>\n" );
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