document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=936000>Question 936000</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A research assistant made 160 mg of radioactive sodium (Na^24) and found that there was only 20 mg left 45 h later.\r<BR>\n" );
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document.write( "(a) What is the half-life of Na^24?\r<BR>\n" );
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document.write( "(b) If the laboratory requires 100 mg of Na^24 12 hours from now, how much Na^24 should the research assistant make now? (Ignore the 20mg she currently has)<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 #569409 by </B><A HREF=/tutors/aboutme.mpl?userid=josgarithmetic><B>josgarithmetic(39620)</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=569409\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> General model is <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=N=N%5Bo%5De%5E%28-kt%29 ALIGN=MIDDLE  ALT=\"N=N%5Bo%5De%5E%28-kt%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=ln%28N%29=ln%28N%5Bo%5D%29-kt ALIGN=MIDDLE  ALT=\"ln%28N%29=ln%28N%5Bo%5D%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%28N%29-ln%28N%5Bo%5D%29=-kt ALIGN=MIDDLE  ALT=\"ln%28N%29-ln%28N%5Bo%5D%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=kt=ln%28N%5Bo%5D%29-ln%28N%29 ALIGN=MIDDLE  ALT=\"kt=ln%28N%5Bo%5D%29-ln%28N%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=k=%281%2Ft%29ln%28N%5Bo%5D%2Fln%28N%29%29 ALIGN=MIDDLE  ALT=\"k=%281%2Ft%29ln%28N%5Bo%5D%2Fln%28N%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >------use this to find the value for k.\r<BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=k=%281%2F45%29%28ln%28160%2F20%29%29 ALIGN=MIDDLE  ALT=\"k=%281%2F45%29%28ln%28160%2F20%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=k=%281%2F45%29ln%288%29 ALIGN=MIDDLE  ALT=\"k=%281%2F45%29ln%288%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=highlight%28k=0.046%29 ALIGN=MIDDLE  ALT=\"highlight%28k=0.046%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >\r<BR>\n" );
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document.write( "You can return to this one, <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=kt=ln%28N%5Bo%5D%29-ln%28N%29 ALIGN=MIDDLE  ALT=\"kt=ln%28N%5Bo%5D%29-ln%28N%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > , to determine the half-life.<BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t=%281%2Fk%29ln%28N%5Bo%5D%2FN%29 ALIGN=MIDDLE  ALT=\"t=%281%2Fk%29ln%28N%5Bo%5D%2FN%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t=%281%2Fk%29ln%282%29 ALIGN=MIDDLE  ALT=\"t=%281%2Fk%29ln%282%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t=%281%2F0.046%29ln%282%29 ALIGN=MIDDLE  ALT=\"t=%281%2F0.046%29ln%282%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=highlight%28t%5Bhalf%5D=15.07%29 ALIGN=MIDDLE  ALT=\"highlight%28t%5Bhalf%5D=15.07%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >, maybe more accuracy than reasonable.\r<BR>\n" );
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document.write( "Your more specific decay model is  <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=N=N%5Bo%5De%5E%28-0.046t%29 ALIGN=MIDDLE  ALT=\"N=N%5Bo%5De%5E%28-0.046t%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >.<BR>\n" );
document.write( "Now you have a known N but you want to solve for <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=N%5Bo%5D ALIGN=MIDDLE  ALT=\"N%5Bo%5D\"   DISABLED_style= \"max-width:90%; height:auto;\" >. </SPAN>\n" );
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