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

  • A. 8
  • B. 7
  • C. 6
  • D. 5

Correct answer: B


  • 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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