document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=441348>Question 441348</A>: <I><SPAN STYLE=\"word-break: break-all;\"> I have no idea how to do this my teacher never taught this type to us. I tried to look in the book but am just so confused with story problems and how to even go about doing this problem.\r<BR>\n" );
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document.write( "The amount remaining of a certain radioactive substance after t days is <BR>\n" );
document.write( "A(t)=A e^(-0.0025t) where A  is the begining amount. How much do we need to <BR>\n" );
document.write( "      0                    0<BR>\n" );
document.write( "begin with if we want 80 grams after 10 days? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #304651 by </B><A HREF=/tutors/aboutme.mpl?userid=ankor@dixie-net.com><B>ankor@dixie-net.com(22740)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=ankor@dixie-net.com><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=ankor@dixie-net.com><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=304651\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> The amount remaining of a certain radioactive substance after t days is<BR>\n" );
document.write( "A(t) = A*e^(-0.0025t) where A is the beginning amount. <BR>\n" );
document.write( "How much do we need to begin with if we want 80 grams after 10 days?<BR>\n" );
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document.write( "write the equation:<BR>\n" );
document.write( " A*e^(-0.0025t) = A(t)<BR>\n" );
document.write( "Given values: <BR>\n" );
document.write( "A(t) = 80<BR>\n" );
document.write( "t = 10<BR>\n" );
document.write( "Replace A(t) and t and we have:<BR>\n" );
document.write( " A*e^(-0.0025*10) = 80<BR>\n" );
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document.write( "A*e^(-0.025) = 80<BR>\n" );
document.write( "Find e^-.025 on a calc, then we have:<BR>\n" );
document.write( ".97531A = 80<BR>\n" );
document.write( "A = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=80%2F.97531 ALIGN=MIDDLE  ALT=\"80%2F.97531\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "A = 82.025 grams will decay to 80 grams in 10 days<BR>\n" );
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document.write( "Check this on a calc: enter: 82.025*e^(-.0025*10): results: 79.9998 ~ 80<BR>\n" );
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document.write( "How about this? Did we shed some light on this stuff for you?\r<BR>\n" );
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document.write( " </SPAN>\n" );
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