Answer
$\large Q=5e^{-0.00693t}$
Work Step by Step
This is an exponential decay problem, with the equation:
$\quad Q=Q_{0}e^{-kt}$
where, $Q_{0}=5$ mg
From the half-life formula, we have:
$ \left\{\begin{array}{ll}
t_{h}k & =\ln 2\\
100k & =\ln 2\\
k & =\dfrac{\ln 2}{100}\approx 0.00693
\end{array}\right.$
Thus, we plug in the $k$ value:
$Q=Q_{0}e^{-kt}$
$\large Q=5e^{-0.00693t}$
