[tex]\bf A=P(1+r)^t\qquad
\begin{cases}
P=\textit{starting amount}\\
r=\textit{rate of change}\\
A=\textit{current amount}\\
t=\textit{elapsed time}\\
--------\\
P=170\\
t=27\\
A=85
\end{cases}\implies 85=170(1+r)^{27}
\\\\\\
\cfrac{85}{170}=(1+r)^{27}\implies \sqrt[27]{\cfrac{1}{2}}=1+r\implies \boxed{\cfrac{1}{\sqrt[27]{2}}-1=r}\\\\
-----------------------------\\\\
A=170\left( 1+\cfrac{1}{\sqrt[27]{2}}-1 \right)^t \iff A=170\left( \cfrac{1}{\sqrt[27]{2}} \right)^t[/tex]
how many mgs after 49hrs? well, set t = 49, to see how much A is there
