document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=998821>Question 998821</A>: <I><SPAN STYLE=\"word-break: break-all;\">  The half-life of radioactive lead 210 is 21.7 years.\r<BR>\n" );
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document.write( "a) find an exponential function model for lead 210. <BR>\n" );
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document.write( "b)Estimate how long it will take a sample of 800 grams to decay to 600 grams?\r<BR>\n" );
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document.write( "Thank you so much for your help </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #616573 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=616573\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> The half-life of radioactive lead 210 is 21.7 years. <BR>\n" );
document.write( "a) find an exponential function model for lead 210.<BR>\n" );
document.write( "A(t) = Ao*(1/2)^(x/21.7) \r<BR>\n" );
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document.write( "b)Estimate how long it will take a sample of 800 grams to decay to 600 grams?<BR>\n" );
document.write( "600 = 800*(1/2)^(x/21.7)<BR>\n" );
document.write( "0.75 = (1/2)^(x/21.7)<BR>\n" );
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document.write( "(x/21.7)*log(1/2) = log(0.75)<BR>\n" );
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document.write( "x/21.7 = log(0.75)/log(1/2) = 0.4150<BR>\n" );
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document.write( "x = 21.7*0.4150 = 9.0063<BR>\n" );
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document.write( "Cheers,<BR>\n" );
document.write( "Stan H.<BR>\n" );
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