# How to calculate radius from circumference

The radius of a circle is an important mathematical concept that is often encountered in various geometrical problems as well as in everyday life. In this article, we will be discussing how to calculate the radius of a circle, given its circumference.

Circumference and radius are related through the formula:

C = 2 * π * r

Where:

– C is the circumference of the circle

– r is the radius of the circle

– π (pi) is a mathematical constant, approximately equal to 3.14159

If we know the circumference of a circle, we can easily find out its radius by rearranging this formula and solving for ‘r’:

r = C / (2 * π)

Now that we have our formula for calculating radius from circumference, let’s go through a step-by-step process:

1. Measure the circumference: To begin with, you’ll need to measure the circumference of your circle. You can either use a string or measuring tape to trace along the outer edge of the circle and note down its length.

2. Insert the value of π: Next, you need to use the value of π. Although it is an irrational number with infinite decimal places, for most calculations, using 3.14159 as an approximation is perfectly fine.

3. Divide the circumference by 2π: Now that you have both the circumference and value of π, simply divide your measured value by double of π (2 * 3.14159).

4. Check and round your answer: After performing the division in step 3, you should have your calculated radius value. Review your calculation and round it appropriately according to your specific requirements.

Let’s apply this method using an example:

Suppose we have measured the circumference of a circle to be 31.42 cm. Using our formula r = C / (2 * π), we can calculate the radius:

r = 31.42 cm / (2 * 3.14159)

r ≈ 31.42 cm / 6.28318

r ≈ 5 cm

Thus, the radius of our circle is approximately 5 cm.

In conclusion, calculating the radius of a circle when given its circumference can easily be determined by first measuring the circumference and then dividing it by double of π value. This simple formula allows you to accurately compute the radius in various real-life situations and geometrical problems.