Simple steps for how to find radius from circumference, how to find the circumference, and how to find the area of a circle.
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We will deal with the circle calculation in this article. Various formulas or equations for calculations are presented and the relationships between radius, diameter, area and circumference are shown. Corresponding tasks / exercises with sample solutions are also available on request. This article belongs to our Mathematics section.
We’ll look at a few things about circle calculation in a moment. However, if the following topics do not mean anything to you, you should read them through first. All others can go straight to the circle calculation.
Circle calculation: formulas + examples
How can you perform a calculation on a circle? To do this, let’s take a closer look at a circle. Here you can see: The circle has a center, the boundary of the circle is always the distance “r” away from this center. The following graphic shows you this:
In addition to the radius, there is also the diameter. The diameter is twice as large as the radius. The formula looks like this:
- d = 2 * r
For example, if the radius of a circle is 2 meters, then the diameter is 4 meters.
In addition, the so-called circle number π (pronounced: pi) is required. At school, the number 3.14159 is usually used for π or simply the corresponding key on the calculator.
Circle calculation: area, radius and diameter
Let’s start with the circle calculation. The two formulas for calculating the area of a circle look like this:
- “A” is the area of the circle in square meters
- “π” is the circle number 3.14159
- “r” is the radius of the circle in meters
- “d” is the diameter of the circle in meters
Circle calculation area examples
1. How to find radius from circumference
The area of a circle is 1.2 m 2 . How big is the radius of the circle? Solution: We change the formula for calculating the area so that we can calculate the radius directly. Then we put in the values.
Now let’s look at a few examples of circle calculation, let’s start with area problems.
2. How to find the area of a circle using the radius
The radius of a circle is 0.34 m. The area of the circle is to be calculated with both of the above formulas and equations.
Solution: We put the radius in the first equation and use it to calculate the area. In order to use the second formula, the radius must first be doubled to get the diameter. We put this diameter in the second equation.
3. How to find the circumference of a circle
The circle calculation is also about formulas for the circumference. The two formulas look like this:
- “U” is the circumference of the circle in meters
- “π” is the circle number 3.14159
- “r” is the radius of the circle in meters
- “d” is the diameter of the circle in meters
Circle calculation scope examples
In the following we would like to show you a few examples of calculating circles with these two formulas.
Example 3:
The radius of a circle is 5 meters. Calculate the circumference of the circle.
Example 4:
Another example for calculating a circle: The diameter of a circle is 8 meters. How big is its scope?
