Annulus

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

    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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