document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=403709>Question 403709</A>: <I><SPAN STYLE=\"word-break: break-all;\"> if the half life is 18 years and the initial amount is 139, how much remains after 5 years...: calculus </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #285449 by </B><A HREF=/tutors/aboutme.mpl?userid=richard1234><B>richard1234(7193)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=richard1234><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=richard1234><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=285449\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> The formula for exponential decay is <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=A+=+A%5B0%5D%2Ae%5Ekt ALIGN=MIDDLE  ALT=\"A+=+A%5B0%5D%2Ae%5Ekt\"   DISABLED_style= \"max-width:90%; height:auto;\" > where <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=A%5B0%5D+=+139 ALIGN=MIDDLE  ALT=\"A%5B0%5D+=+139\"   DISABLED_style= \"max-width:90%; height:auto;\" >, k is some constant, and t is time. Also, we have\r<BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=69.5+=+139%2Ae%5E%2818k%29 ALIGN=MIDDLE  ALT=\"69.5+=+139%2Ae%5E%2818k%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > given the half-life\r<BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=1%2F2+=+e%5E%2818k%29 ALIGN=MIDDLE  ALT=\"1%2F2+=+e%5E%2818k%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >\r<BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=18k+=+ln%281%2F2%29+=+ln+%281%29+-+ln+%282%29+=+-ln+%282%29 ALIGN=MIDDLE  ALT=\"18k+=+ln%281%2F2%29+=+ln+%281%29+-+ln+%282%29+=+-ln+%282%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >\r<BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=k+=+%28-ln+%282%29%29%2F18 ALIGN=MIDDLE  ALT=\"k+=+%28-ln+%282%29%29%2F18\"   DISABLED_style= \"max-width:90%; height:auto;\" >\r<BR>\n" );
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document.write( "Now, substitute into your original equation for exponential decay and replace t = 5 years to solve. </SPAN>\n" );
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