On this post, I will show you all the simple way about how to find the radius of a circle quickly.
The radius is the distance from the center of a circle to its circumference/perimeter. It stays same at every angle of the circle. To find the radius of a circle you can rely on very simple steps. Here we will crack every method in an easy way.
How to Find the Radius of a Circle
The first and easiest way to find a radius of any circle is using diameter.
If you extend tow line from the center of a circle and it ends at the boundary of the circle, it would call as the diameter of that circle.
Image of diameter
You can get the diameter by placing your ruler at the center of the circle. Once you have got the diameter use this formula to find the radius of the circle.
Radius = Diameter / 2
Here’s an example.
Suppose, the diameter of a circle is 10 centimeters.
Then, Radius = 10 centimeter / 2 = 4 centimeter
Done! The radios of the circle are 4 centimeters. Make sure that you keep in mind the provided units.
Find the Radius of a Circle using Circumference
What if you have the only circumference of a circle? Still, you can solve the radius out of it. Basically, the circumference is called as the perimeter of a circle.
To get the radius of a circle using circumference, follow those steps one-by-one.
Step 1: Note the Circumference value
At first, take a note on the value of the circumference value of the circle. Because we will use this value to solve the radius of the circle.
Step 2: Divide the Circumference with 2
When you know the circumference value, just divide the circumference of the circle with 2. Here’s an example.
If the circumference is 50, then after dividing with 2 you will get = 50 / 2 = 25
Step 3: Divide the Circumference with Pie
Well, after getting the new value of circumference, you have to divide it with Pie(π). The value of Pie(π) is 3.14.
Just like we have got 25 from the last step. Now you have to follow this formula with it.
25 / π = 7.96
You have got the radius of the circle, it’s 7.96. Well, you may have to use a calculator to solve this calculation.
Find the Radius of a Circle using Area
You can also find the radius of a circle from its area. It’s not that easy but if you try it’s quite simple to solve.
Step 1: Note the Area value
Make sure that you have noted the aciculate value of Area. Always remember that when you get Area of a circle it would be always in square2 format. Just like 50 ft2 (square feet)
Step 2: Divide the Area with Pie
When you get the Area of a circle, just divide it with Pie(π). The value of Pie(π) is around 3.14.
Here’s an example,
50 / π = 15.9
Take a note of what you get after dividing it with Pie. We will need it, in the next step.
Step 3: Do Square Root
The result you have got from the previews steps, you have to square root it.
Just like, √15.91 = 3.9
So, the radius of the circle is 3.9 square foot. You have found it from the Area of the circle.
Find the Radius of a Circle using Volume
You can also use a circle’s volume to find it’s radius. The volume refers to the internal space of a circle or globe. The volume is a mixture of height, width, and length of the circle.
However, if you have the volume of a circle you can get the radius with those steps.
Step 1: Note the Volume
At first, note down the correct volume of your circle. We will formulate its value to get the radius.
The value of volume always would be in cube3 format.
Step 2: Multiply the Volume with ¾
Once you have the volume you have to multiply the value with 3/4. If you have 500 inc3, just use this formation.
500 x ¾ = 375
Take a note of the value you have got. We will use this at the next step.
Step 3: Divide with Pie
Now, divide the result you have got with Pie(π). The value of Pie(π) is considered as 3.14.
375 / π = 119.4
Wait! It hasn’t done yet. You have done go through another step to get the radius of the circle.
Step 4: Do Cube Root
Lastly, you have to cube root the result you have got from the last step. In this example, you had 119.4. So, follow the below example.
√199.43 = 5.8
We have got the radius of the circle using its volume. But, don’t forget to carry the given unit with its result.
So, that’s how to find the radius of a circle from its diameter, Area, and Volume. It’s not that difficult if you practice it perfectly. Although, you may get other problems to solve as you go deeper. Drop your question in the comment box.