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How to Find the Radius of a Cone

by Chance E. Gartneer, Demand Media

    A cone is a three-dimensional object with a circular base. As the cone grows upward, the size of the circle lessens until it becomes a single point at the top of the cone. A radius is the distance from the circle's middle to its perimeter, which is known as its circumference. The radius of a cone is the radius of its circular base. You can find a radius through its volume and height.

    Items you will need

    • Calculator
    Step 1

    Multiply the volume by 3. For example, the volume is 20. Multiplying 20 by 3 equals 60.

    Step 2

    Multiply the height by π, which is a numeric constant that begins 3.14 and never terminates. For this example, the height is 4, and 4 multiplied by π equals 12.566.

    Step 3

    Divide the tripled volume by the product of the height and π. For this example, 60 divided by 12.566 equals 4.775.

    Step 4

    Find the square root of the result from Step 3. For this example, the square root of 4.775 equals 2.185. The radius is 2.185.

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    References

    • "Basic Math and Pre-algebra"; Jerry Bobrow; 1995
    • "The Complete Idiot's Guide to Geometry"; Denise Szecsei; 2004

    About the Author

    Chance E. Gartneer began writing professionally in 2008 working in conjunction with FEMA. He has the unofficial record for the most undergraduate hours at the University of Texas at Austin. When not working on his children's book masterpiece, he writes educational pieces focusing on early mathematics and ESL topics.

    Photo Credits

    • Thinkstock/Comstock/Getty Images

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