document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1048802>Question 1048802</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Please help me with this question.\r<BR>\n" );
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document.write( "2. The rate of decay of a radioactive substance is 0.1% per year.<BR>\n" );
document.write( "(a) Find the half-life of the substance.<BR>\n" );
document.write( "(b) How long would it take until only 1/2 of the amount remains?<BR>\n" );
document.write( "(c) How long would it take until 2/3 of the original amount decays?<BR>\n" );
document.write( "(d) How much of the 10 mg sample of the substance will remain after<BR>\n" );
document.write( "5,000 years? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #664372 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=664372\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\">  The rate of decay of a radioactive substance is 0.1% per year.<BR>\n" );
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document.write( "(a) Find the half-life of the substance.<BR>\n" );
document.write( "A(t) = Ao(0.999)^t<BR>\n" );
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document.write( "(b) How long would it take until only 1/2 of the amount remains?\r<BR>\n" );
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document.write( "(1/2)Ao = Ao(0.999)^t<BR>\n" );
document.write( "0.999^t = (1/2)<BR>\n" );
document.write( "t = log(0.5)/log(0.999) = 692.8 years<BR>\n" );
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document.write( "(c) How long would it take until 2/3 of the original amount decays?<BR>\n" );
document.write( "t = log(2/3)/log(0.999) = 405.26 years<BR>\n" );
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document.write( "(d) How much of the 10 mg sample of the substance will remain after<BR>\n" );
document.write( "5,000 years?<BR>\n" );
document.write( "A(5000) = 10*0.999^5000<BR>\n" );
document.write( "A(5000) = 0.0672 mg<BR>\n" );
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document.write( "Cheers,<BR>\n" );
document.write( "Stan H.<BR>\n" );
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document.write( " </SPAN>\n" );
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