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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).

Example 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.

Solved Example on Annulus

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.]

Related Terms for Annulus

• Area
• Circle
• Concentric
• Radius

Additional Links for Annulus

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