Finding the circumference of a circle is a common task in mathematics, and many real-life situations require it. You can find a circle's circumference, which is the measure of the distance around the circle, if you know either the radius or the diameter of the circle.
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Difficulty:
Moderately Easy
Instructions
1
Measure the diameter of the circle. The diameter is the distance across the circle through its center. The diameter is also twice the radius, which is the distance from the center of the circle to the circle's edge.
2
Apply the formula for finding the circumference of a circle, using the measure of the diameter from step one. The formula is C =π x d , or in words, the circumference equals π multiplied times the diameter. The symbol π stands for the number pi, whose value is approximately 3.14, d stands for the diameter of the circle and the x is a mathematical symbol for multiplication.
3
Substitute the measurement from step one into the formula. Suppose the measure of the diameter is 5 inches. The formula would look like this: C = π x 5 inches.
4
Substitute 3.14 for π in the formula and do the computation. Here's how it looks in the formula: C = 3.14 x 5 inches, and the result is 15.70 inches. This number is the circumference of a circle whose diameter is 5 inches.
Tips & Warnings
If you're finding the circumference of a circle whose measurements are known (as in a problem from a book), you'll need to skip step one. Just use the given measurements and start with step two.
Don't be confused if you see the formula for the circumference of a circle written slightly different from that in step two. Sometimes it's written as C = 2 x π x r, where r stands for the radius of the circle. This is equivalent to C = π x d, because the diameter of a circle is two times the radius.
Calculating a circle's arc length, central angle, and circumference are not just tasks, but are essential skills for geometry, trigonometry, and beyond....
