What is an example of a decay practice problem?

Suppose a sample has a half-life of $60$ seconds. Then let's say $5$ hours passed by. If we start with ${\left[A\right]}_{0}$ initial concentration of the sample, what is the final concentration, $\left[A\right]$, expressed in terms of ${\left[A\right]}_{0}$?
You should get that since $300$ half-lives passed, $\left[A\right] = {\left(\frac{1}{2}\right)}^{300} {\left[A\right]}_{0}$.