document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=253874>Question 253874</A>: <I><SPAN STYLE=\"word-break: break-all;\"> beryllium-11 decomposes into boron-11 with a half life of 13.8 seconds.  How long will it take 240 g of beryllium-11 to decompose into 7.5g of beryllium-11? \r<BR>\n" );
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document.write( "based on the forumula provided in the text book C(t)=C(0)2e^-t/h\r<BR>\n" );
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document.write( "where C(0) = 240, C(t)=7.5 ,h=13.8\r<BR>\n" );
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document.write( "7.5/240=2e^-t/13.8\r<BR>\n" );
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document.write( "this was a s far as i got </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #356926 by </B><A HREF=/tutors/aboutme.mpl?userid=martin.jabou><B>martin.jabou(1)</B></A><img src=\"/images/stars/iconNewId_16x16.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=martin.jabou><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=356926\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> The solution is quite simple actually:\r<BR>\n" );
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document.write( "You know you are going from 240g of Be-11 to 7.5g of Be-11, so write down what you have - \r<BR>\n" );
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document.write( "Half Life Formula is C(t) = Cø2^(-t/H)\r<BR>\n" );
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document.write( "C(t) = 7.5g, Cø = 240g, H = 13.8 seconds\r<BR>\n" );
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document.write( "Sub In:\r<BR>\n" );
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document.write( "7.5 = 240 (2)^(-t/H) \r<BR>\n" );
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document.write( "Divide both sides by 240 to get:\r<BR>\n" );
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document.write( "7.5 / 240 = 2^(-t/13.8)\r<BR>\n" );
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document.write( "Simplify:\r<BR>\n" );
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document.write( "1 / 32 = 2^(-t/13.8)\r<BR>\n" );
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document.write( "1 / 32 must be written as a base two: therefore it becomes 2 ^ -5, your new equation is:\r<BR>\n" );
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document.write( "2^-5 = 2^(-t/13.8)\r<BR>\n" );
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document.write( "Since at this point you have the same base 2 on both sides, you can now equate the exponents to each other and solve for variable t. You get:\r<BR>\n" );
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document.write( "-5 / 1 = -t/13.8\r<BR>\n" );
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document.write( "-69 = - t, divide each side by -1 (not particularly necessary since we know time cannot be negative) and we get T is equal to 69 seconds :)  </SPAN>\n" );
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