Annulus
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Definition of Annulus
Annulus is the area between the two concentric circles having different radii.
More About Annulus
 A ringshaped 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(R^{2}  r^{2}).
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 cmB. 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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