document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1080195>Question 1080195</A>: <I><SPAN STYLE=\"word-break: break-all;\"> I dont understand whats a half life? How do i get this answer?\r<BR>\n" );
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document.write( " The amount of carbon 14 in a given organism at the time of that organism’s death (time zero) is 100%.<BR>\n" );
document.write( "The half-life of carbon 14 is 5750 years, which means only 50% of the original carbon 14 will remain in<BR>\n" );
document.write( "the given object 5750 years later. How old is an object that is found to contain only 20% of its original<BR>\n" );
document.write( "carbon 14, to the nearest ten years?\r<BR>\n" );
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document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #694384 by </B><A HREF=/tutors/aboutme.mpl?userid=rothauserc><B>rothauserc(4718)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=rothauserc><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=rothauserc><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=694384\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> carbon-14 is a radioactive isotope of carbon, half-life is the time for half the carbon-14 in an object to decay into nitrogen-14.<BR>\n" );
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document.write( "The appropriate formula is<BR>\n" );
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document.write( "A = Ao x (1/2)^(t / HL), A is the amount currently remaining, Ao is the original amount, t is the amount of time that has passed, and HL is the half-life<BR>\n" );
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document.write( "0.20 = 1.00 x (1/2)^(t / 5750)<BR>\n" );
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document.write( "0.20 = (1/2)^(t / 5750)<BR>\n" );
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document.write( "use definition of logarithm<BR>\n" );
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document.write( "(t / 5750) = log base (1/2) 0.20 = 2.3219<BR>\n" );
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document.write( "t = 5750 * 2.3219 = 13350.925<BR>\n" );
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document.write( "The object is 13,350 years old<BR>\n" );
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