Check the picture below.
[tex]\textit{area of a circular ring}\\\\ A=\pi (R^2-r^2)~~ \begin{cases} r=\stackrel{smaller}{radius}\\ R=\stackrel{larger}{radius}\\[-0.5em] \hrulefill\\ r=2\\ R=3 \end{cases}\implies \begin{array}{llll} A=\pi (3^2-2^2)\implies A=5\pi \\\\\\ A\approx 15.71 \end{array}[/tex]
