document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=92097>Question 92097</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Find the exponential decay function for a radioactive material that has a half-life of 1234 years. How long will it take until only 10% of the material remains? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #66934 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=66934\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Find the exponential decay function for a radioactive material that has a half-life of 1234 years. How long will it take until only 10% of the material remains?<BR>\n" );
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document.write( "A(t) = A(o)(1/2)^(t/1234)<BR>\n" );
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document.write( "0.10A(o) = A(o)(1/2)^(t/1234)<BR>\n" );
document.write( "0.10 = (1/2)^(t/1234)<BR>\n" );
document.write( "Take the log of both sides to get:<BR>\n" );
document.write( "log0.10 = (t/1234)log(1/2)<BR>\n" );
document.write( "t/1234 = [log0.10]/[log(1/2) = 3.321928095...<BR>\n" );
document.write( "t = 4099.259269 years<BR>\n" );
document.write( "===============<BR>\n" );
document.write( "Cheers,<BR>\n" );
document.write( "Stan H. </SPAN>\n" );
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