Definition Of Annulus

Annulus is the area between the two concentric circles having different radii.

More About Annulus

A ring-shaped object is called as 'annulus' in Latin.
Area (A) between two concentric circles with outer radius R and inner radius r is given by, A = Π(R² - r²).

Examples of Annulus

Two concentric circles with outer radius R and inner radius r are shown in the figure. The region shaded with green color is annulus.

Video Examples: Area of an Annulus

Solved Example Clockple on Annulus

Ques: Find the area enclosed between the two concentric circles of radii 8 cm and 10 cm.

Choices:

A. 38Π square cm
B. 37Π square cm
C. 36Π square cm
D. 40Π square cm
Correct Answer: C

Solution:

Step 1: Required Area = Area of outer circle - Area of inner circle
Step 2: Required Area = Π(10)² - Π(8)² [Use circle area formula and substitute.]
Step 3: Required Area = Π(100 - 64) = 36Π square cm [Simplify.]

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