How Do You Find the Surface Area of a Sphere?


Quick Answer

To find the surface area of a sphere, use the formula 4(pi)r2. In this formula, r is equivalent to the radius. Pi represents the infinite number 3.141592..., which is usually rounded to 3.14.

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Full Answer

In geometry, a sphere is defined as a perfectly round, three-dimensional object. A smooth round ball, such as a Ping-Pong ball, is a perfect example of a sphere. The radius of a sphere is the measurement from the center point out to a point on the surface of the sphere. Once a person knows the radius, it is simple to calculate the surface area, sometimes referred to as the "curved surface area," or CSA.

  1. Write out the equation
  2. Plug the measurement of the radius into the equation for the CSA. For example, if the radius is 3 centimeters, then the equation is written as: CSA = 4(3.14)(32).

  3. Square the radius
  4. Before attempting any other multiplication, square the radius and rewrite the equation with that number. In the example given, 32 is equal to 3 x 3, or 9. Rewritten, the equation is: CSA = 4(3.14)(9).

  5. Multiply the rest of the equation
  6. To complete the equation and find the radius, multiply from left to right. Using the equation given, first multiply 4 x 3.14 to get 12.56, and then multiply 12.56 x 9 to get 113.04.

  7. Remember the units
  8. Do not forget to include the units in the final answer. In the example, the units were centimeters. Therefore, the final answer is 113.04 square centimeters.

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