To convert the depreciation percentage to a decimal, you simply divide the percentage by $100.$ So$,50\%$ becomes $0\mathrm{.}5.$

For the formula $\backslash ($ A $=$ P$(1+$ r$)^$t $\backslash ),$ where $\backslash ($ A $\backslash )$ is the amount, $\backslash ($ P $\backslash )$ is the initial value, $\backslash ($ r $\backslash )$ is the annual depreciation rate, and $\backslash ($ t $\backslash )$ is the number of years, if the depreciation rate is given as a percentage, we convert it to a decimal.

If $\backslash ($ r $\backslash )$ is the depreciation rate as a decimal, it is represented as a negative value since it's decreasing over time. For example, if the depreciation rate is $\backslash (0\mathrm{.}05\backslash ),$ it means $\backslash (5\backslash \%\backslash )$ depreciation annually.

So$,$ if you have $\backslash (50\backslash \%\backslash )$ depreciation, as you stated, it becomes $\backslash (0\mathrm{.}5\backslash )$ when expressed as a decimal. If you're using the formula $\backslash ($ A $=$ P$(1+$ r$)^$t $\backslash ),$ then $\backslash ($ r $\backslash )$ would be $\backslash (-0\mathrm{.}5\backslash )$ to represent a $\backslash (50\backslash \%\backslash )$ annual decrease.

Let me know if you'd like to proceed with a specific calculation or further explanation!