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Area of a Ring (Annulus)
A = π(R² − r²) = π(R + r)(R − r)
Where: A = Area, R = outer radius, r = inner radius
Use the same units for all lengths (e.g. all in cm); areas come out in cm², volumes in cm³.
Solved example
Given: R = 7, r = 5
Find: A (Area)
- Formula: A = π·(R² - r²)
- Substitute the values: A = π·(-5² + 7²)
- Result: A = 75.398224
Answer: A = 75.398224
Calculator
How to calculate Area of a Ring (Annulus)
- Write down the formula: A = π(R² − r²) = π(R + r)(R − r).
- Note the known values (R, r).
- Substitute them and simplify to find A.
- Use the calculator above to solve for any letter.
Frequently asked questions
What is the formula for Area of a Ring (Annulus)?
The formula is A = π(R² − r²) = π(R + r)(R − r), where A = Area, R = outer radius, r = inner radius.
What is Area of a Ring (Annulus) when R = 7, r = 5?
A = 75.398224. Substitute the values into A = π(R² − r²) = π(R + r)(R − r) and simplify.