document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=957506>Question 957506</A>: <I><SPAN STYLE=\"word-break: break-all;\"> The half-life of an isotope is the time for its mass to decay by ½.  For example, polonium-210 has a half-life of 40. So, a sample of 100 g would decay to 50 g in 40 weeks.  The percent, P, of polonium remaining after t weeks is given by the formula  .  What percent of polonium remains after 30 weeks?Show your work for full marks.  (2 mark)<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 #585119 by </B><A HREF=/tutors/aboutme.mpl?userid=josgarithmetic><B>josgarithmetic(39617)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=josgarithmetic><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=585119\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> \"The formula\" might be P=Ie^(-kt) where I is the initial percent of polonium.  What is not clear is your description for half-life.  40 WHAT?\r<BR>\n" );
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document.write( "Half-life of polonium 210 is 138.4 days.  What is the unit of \"40\"?  This is unclear.\r<BR>\n" );
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document.write( "Ordinarily, advice would be use half-life information to find the k value, and then solve the question part of the problem  using this k value.\r<BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=highlight%28P=Ie%5E%28-kt%29%29 ALIGN=MIDDLE  ALT=\"highlight%28P=Ie%5E%28-kt%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=ln%28P%29=ln%28I%29-kt ALIGN=MIDDLE  ALT=\"ln%28P%29=ln%28I%29-kt\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=ln%28P%2FI%29=-kt ALIGN=MIDDLE  ALT=\"ln%28P%2FI%29=-kt\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=highlight_green%28k=ln%28I%2FP%29%2Ft%29 ALIGN=MIDDLE  ALT=\"highlight_green%28k=ln%28I%2FP%29%2Ft%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > </SPAN>\n" );
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