how do you find the arc length for $\newcommand{arc}[1]{\stackrel{\Large\frown}{#1}}\arc{PQR}$? 

I know $\newcommand{arc}[1]{\stackrel{\Large\frown}{#1}}\arc{PQ}$ is $8.1$ do I just $8.1+8.1$ to find $\newcommand{arc}[1]{\stackrel{\Large\frown}{#1}}\arc{PQR}$? 

[![enter image description here](https://i.stack.imgur.com/S4YM2.jpg)](https://i.stack.imgur.com/S4YM2.jpg)