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How to Calculate the Area of a Circle Using the Radius

Learn to find the area of a circle using the radius with the formula A = πr². Discover key details in our short Q&A.

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Video transcript

To find the area of a circle without the diameter, use the formula A = πr², where A is the area, and r is the radius. If you have the radius (r), simply substitute it into the formula and multiply π (approx. 3.14159) by the square of the radius. For example, if the radius is 5 units, the area is A = π 5² = π 25 ≈ 78.54 square units.

Questions and answers

  1. What formula is used to find the area of a circle?

    The formula to find the area of a circle is A = πr², where r is the radius.

  2. Can you calculate the area without the diameter?

    Yes, you can calculate the area using the radius directly with the formula A = πr².

  3. What does A represent in the circle area formula?

    In the formula A = πr², A represents the area of the circle.

  4. How do you find the radius if you have the area?

    To find the radius from the area, rearrange the formula: r = √(A/π).

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