document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=812540>Question 812540</A>: <I><SPAN STYLE=\"word-break: break-all;\"> The half life of radioactive element plutonium-239 is 20 years.<BR>\n" );
document.write( "How long will it take for a sample of this substance to decay to 60% of its original amount? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #489283 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=489283\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> The half life of radioactive element plutonium-239 is 20 years.<BR>\n" );
document.write( "How long will it take for a sample of this substance to decay to 60% of its original amount?<BR>\n" );
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document.write( "The radioactive decay formula: A = Ao*2^(-t/h), where:<BR>\n" );
document.write( "A = resulting amt after t time<BR>\n" );
document.write( "Ao = initial amt (t=0)<BR>\n" );
document.write( "t = time of decay<BR>\n" );
document.write( "h = half-life of substance<BR>\n" );
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document.write( "Let initial amt = 1<BR>\n" );
document.write( "2^(-t/20) = .6<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=-t%2F20 ALIGN=MIDDLE  ALT=\"-t%2F20\"   DISABLED_style= \"max-width:90%; height:auto;\" > = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=log%28.6%29%2Flog%282%29 ALIGN=MIDDLE  ALT=\"log%28.6%29%2Flog%282%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "t = -.7369656 * -20<BR>\n" );
document.write( "t = 14.74 yrs </SPAN>\n" );
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