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Circumference of a circle


As seen in the the number pi, the formula for the circumference of a circle is

C = 2 × pi × r

If r is known, simply substitute the known value for r in the formula. Use 3.14 for pi.

Examples:

1) Calculate C if r = 2 inches

C = 2 × pi × r = 2 × 3.14 × 2 = 12.56 inches

2) Calculate C if r = 4 inches

C = 2 × pi × r = 2 × 3.14 × 4 = 25.12 inches

3) If C = 50.24 inches, calculate r.

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Use the calculator below to practice


Enter the radius of the circle:     

       

The circumference is :  



Fun math game: Destroy numbered balls by adding to 10







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