Question 1190047
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The formula is  


    y = {{{31.9*(1/2)^(t/9)}}}.


Notice that 31.9 is the initial amount at the beginning  (t= 0).


The denominator "9" in the index of the exponential function is the half-life time 9 minutes.


t is the current time in minutes.


To calculate remaining mass at t= 14 minutes,  substitute t= 14 into the formula and compute.
</pre>

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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> 

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



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



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