document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=613570>Question 613570</A>: <I><SPAN STYLE=\"word-break: break-all;\"> The half-life of tritium is 12.4 years. How long will it take for 20% of a sample of tritium to decompose?<BR>\n" );
document.write( "Please round the answer to the nearest tenth. \r<BR>\n" );
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document.write( "-log5= -t/12.4 log2 -->  12.4(log5\log2)=t --> t=28.8<BR>\n" );
document.write( "I know this is incorrect </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #386073 by </B><A HREF=/tutors/aboutme.mpl?userid=jim_thompson5910><B>jim_thompson5910(35256)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=jim_thompson5910><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=386073\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> N = P*e^(-kt)\r<BR>\n" );
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document.write( "1/2P = P*e^(-k*12.4)\r<BR>\n" );
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document.write( "1/2 = e^(-12.4k)\r<BR>\n" );
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document.write( "ln(1/2) = -12.4k\r<BR>\n" );
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document.write( "-0.693147 = -12.4k\r<BR>\n" );
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document.write( "-0.693147/(-12.4) = k\r<BR>\n" );
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document.write( "0.05589895 = k\r<BR>\n" );
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document.write( "k = 0.05589895\r<BR>\n" );
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document.write( "N = P*e^(-kt)\r<BR>\n" );
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document.write( "N = P*e^(-0.05589895t)\r<BR>\n" );
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document.write( "0.8P = P*e^(-0.05589895t)\r<BR>\n" );
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document.write( "0.8 = e^(-0.05589895t)\r<BR>\n" );
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document.write( "ln(0.8) = -0.05589895t\r<BR>\n" );
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document.write( "-0.22314355 = -0.05589895t\r<BR>\n" );
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document.write( "-0.22314355/(-0.05589895) = t\r<BR>\n" );
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document.write( "3.9919095 = t\r<BR>\n" );
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document.write( "t = 3.9919095\r<BR>\n" );
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document.write( "So it will take roughly 3.9919095 years for 20% of the sample to decompose. </SPAN>\n" );
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