Compute the area of an annulus (ring) from the outer and inner radii.
An annulus is the region between two concentric circles. Its area is the difference of the two circle areas: π(R² − r²).
Annulus Area
A = π(R² − r²)
Then the annulus becomes a full circle with area πR².
Yes — divide each diameter by 2 to get the corresponding radius, then apply the formula.