How to Calculate Annulus Area
What is Annulus Area?
An annulus is a ring-shaped region between two concentric circles. The area calculation subtracts the inner circle from the outer circle, useful in engineering and architecture.
Formula
Area = π(R² - r²) where R is outer radius and r is inner radius
Step-by-Step Guide
- 1Enter the outer radius R
- 2Enter the inner radius r
- 3Calculate π(R² - r²)
Worked Examples
Input
R = 10 cm, r = 6 cm
Result
Area ≈ 201 cm²
π(100 - 36) ≈ 201
Common Mistakes to Avoid
- ✕Reversing outer and inner radii
- ✕Using diameter instead of radius
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