[tex]\bf A=P\left(1+r\right)^{t}
\quad
\begin{cases}
A=\textit{accumulated amount}\\
P=\textit{starting amount}\to &\$85\\
r=rate\to 100\%\to \frac{100}{100}\to &1.00\\
t=time\to 3hrs\to &6
\end{cases}
\\\\\\
A=85(1+1)^6[/tex]
now, bear in mind that, the population is doubling every half-hour, so, in 3hrs, it doubled 6 times, thus, our time is 6 for 3hrs, since the cycle is every 30mins
now, for 24hrs? well, that's 48 half-hours, thus t = 48
[tex]\bf A=85(1+1)^{48}[/tex]
