Definition Of Radius

Radius is the distance from the center of a circle or a sphere to any point on the circle or a sphere.

In other words, radius is a line segment joining the center of a circle with any point on the circle.

Examples of Radius

 is a radius of the circle shown. 

Video Examples: How to Find a Radius Between Two Points

Solved Example on Radius

Ques: Find the radius of a circle with area 153.86 square inches. Take π = 3.14

Choices:

A. 8
B. 7
C. 6
D. 5

Correct answer: B

Solution:

Step 1: Area of a circle of radius r = π r² [Original equation.]
Step 2: 153.86 = 3.14 r² [Substitute values.]
Step 3:  [Divide each side by 3.14.]
Step 4: 49 = r² [Simplify.]
Step 5:  [ Evaluate square root on both sides.]
Step 6: r = 7 [Ignore the negative value.]

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