document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1088727>Question 1088727</A>: <I><SPAN STYLE=\"word-break: break-all;\"> After the release of radioactive material into the atmosphere from a nuclear power plant in a country in 1988&#8203;, the hay in that country was contaminated by a radioactive isotope&#8203; (half-life 6 &#8203;days). If it is safe to feed the hay to cows when 14&#8203;% of the radioactive isotope&#8203; remains, how long did the farmers need to wait to use this&#8203; hay?\r<BR>\n" );
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document.write( "The farmers needed to wait approximately ____ days for it to be safe to feed the hay to the cows?\r<BR>\n" );
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document.write( "&#8203;(Round to one decimal place as&#8203; needed.) </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #703233 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=703233\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> After the release of radioactive material into the atmosphere from a nuclear power plant in a country in 1988&#8203;, the hay in that country was contaminated by a radioactive isotope&#8203; (half-life 6 &#8203;days).<BR>\n" );
document.write( " If it is safe to feed the hay to cows when 14&#8203;% of the radioactive isotope&#8203; remains, how long did the farmers need to wait to use this&#8203; hay?<BR>\n" );
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document.write( "using the radioactive decay formula: A = Ao*2^(-t/h), where<BR>\n" );
document.write( "A = remaining amt after t time<BR>\n" );
document.write( "Ao = initial amt<BR>\n" );
document.write( "t = time of decay<BR>\n" );
document.write( "h = half-life of substance<BR>\n" );
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document.write( "let initial amt = 1<BR>\n" );
document.write( "then<BR>\n" );
document.write( "resulting amt = .14 <BR>\n" );
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document.write( "1*2^(-t/6) = .14<BR>\n" );
document.write( "use nat logs<BR>\n" );
document.write( "ln(2^(-t/6)) = ln(.14)<BR>\n" );
document.write( "the log equiv of exponents<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=-t%2F6 ALIGN=MIDDLE  ALT=\"-t%2F6\"   DISABLED_style= \"max-width:90%; height:auto;\" >*ln(2) = ln(.14<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=-t%2F6 ALIGN=MIDDLE  ALT=\"-t%2F6\"   DISABLED_style= \"max-width:90%; height:auto;\" > = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=ln%28.14%29%2Fln%282%29 ALIGN=MIDDLE  ALT=\"ln%28.14%29%2Fln%282%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "using your calc we have<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=-t%2F6 ALIGN=MIDDLE  ALT=\"-t%2F6\"   DISABLED_style= \"max-width:90%; height:auto;\" > = -2.8365<BR>\n" );
document.write( "multiply both sides by -6<BR>\n" );
document.write( "t = 17.02 days before using the hay<BR>\n" );
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