Question 1187771
.
The half life of a sodium is 15 hours. How long does it take for 95% of a sample of this
isotope to decay?
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<pre>
If 95% of the material decayed, it means that 5% of the material remained.


So we write the decay equation in terms of half-life


    0.05 = 0.5^(t/15),


where "t" is the sough time, in hours.


Next we take the logarithm base 10 from both sides


    log(0.05) = {{{(t/15)*log((0.5))}}},


and we get the <U>ANSWER</U>


    t = {{{(15*log((0.05)))/log((0.5))}}} = use your calculator = 64.82892142 hours = 64.829 hours (rounded).
</pre>

Solved.


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On radioactive decay, &nbsp;see the lesson

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=https://www.algebra.com/algebra/homework/logarithm/Radioactive-decay-problems.lesson>Radioactive decay problems</A> 

in this site.


You will find many similar &nbsp;(and different) &nbsp;solved problems there.



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Also, &nbsp;you have this free of charge online textbook in &nbsp;ALGEBRA-I &nbsp;in this site

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=https://www.algebra.com/algebra/homework/quadratic/lessons/ALGEBRA-I-YOUR-ONLINE-TEXTBOOK.lesson>ALGEBRA-I - YOUR ONLINE TEXTBOOK</A>.


The referred lesson is the part of this online textbook under the topic "<U>Logarithms</U>".



Save the link to this online textbook together with its description


Free of charge online textbook in ALGEBRA-I
https://www.algebra.com/algebra/homework/quadratic/lessons/ALGEBRA-I-YOUR-ONLINE-TEXTBOOK.lesson


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