document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=199966>Question 199966</A>: <I><SPAN STYLE=\"word-break: break-all;\"> 5.	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 dont get these problems can anyone help? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #150332 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=150332\">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. <BR>\n" );
document.write( "A meteorite is discovered to have only 8.6% of its original thorium remaining.<BR>\n" );
document.write( " How old is the meteorite?<BR>\n" );
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document.write( "The half life equation<BR>\n" );
document.write( " Ao*(2^(-t/h)) = A<BR>\n" );
document.write( "Where<BR>\n" );
document.write( "A = resulting amt <BR>\n" );
document.write( "Ao - initial amt<BR>\n" );
document.write( "t = time <BR>\n" );
document.write( "h = half-life of the substance<BR>\n" );
document.write( ":<BR>\n" );
document.write( "Time in this problems is millions of yrs:<BR>\n" );
document.write( "Let Ao = 100<BR>\n" );
document.write( "then<BR>\n" );
document.write( "A = 8.6<BR>\n" );
document.write( "h = 2 (million yrs)<BR>\n" );
document.write( "Find t in millions of yrs<BR>\n" );
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document.write( "100(2^(-t/2)) = 8.6<BR>\n" );
document.write( "2^(-t/2) = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=8.6%2F100 ALIGN=MIDDLE  ALT=\"8.6%2F100\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "2^(-t/2) = .086<BR>\n" );
document.write( ":<BR>\n" );
document.write( "log(2^(-t/2)) = log(.086)<BR>\n" );
document.write( ";<BR>\n" );
document.write( "log equiv of exponents<BR>\n" );
document.write( "<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;\" >log(2) = log(.086)<BR>\n" );
document.write( ":<BR>\n" );
document.write( "find the logs<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%28-.301t%29%2F2 ALIGN=MIDDLE  ALT=\"%28-.301t%29%2F2\"   DISABLED_style= \"max-width:90%; height:auto;\" > = -1.0655<BR>\n" );
document.write( "Multiply equation by 2<BR>\n" );
document.write( "-.301t = 2(-1.0655)<BR>\n" );
document.write( ":<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 = 7.078 million years<BR>\n" );
document.write( ":<BR>\n" );
document.write( ":<BR>\n" );
document.write( "Check solution on calc: enter: 2^(-7.078/2)*100 = 8.6%\r<BR>\n" );
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document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );