 # Circle Formula

We may have come across many objects in our daily life which is round in shape. Some objects of this shape are wheels of a vehicle, bangles, dials of clocks, coins, etc. In a clock, we have observed that the second’s hand goes around the dial of the clock. It is making a round path around the fixed pivot. This pivot is known as a circle. This path traversed by the tip of the second’s hand is called a circle. In this article, we will discuss circles, some other related terms and circle formula with examples. Let’s start learning!

## Circle Formula

### What is a circle?

A circle is a particular shape of the objects. A circle is a type of closed shape. It is the set of all points in a plane that are at a given distance from a given point. So, it is the curve traced out by a point that moves in a plane in such a way so that its distance from the given point is constant.

It is defined as the set of points in a plane placed at the equal distance from a single pivot point, called the center of the circle. It is a fact that the circle represents a two-dimensional plane. Its three-dimensional figure is known as a sphere. In this shape, no vertex or edge exists.

### Some terms related to this shape are as follows:

1. Center: It is a point as a pivot in the circle. It is used to draw the circle.
2. Circumference: It is the set of points that are at equal distance around the center of the circle.
3. Radius: It is the distance from the center to any point on the circumference.
4. Diameter: It is the distance between any two points on the circumference measured through the center. It is double in the length that the length of the radius.
5. Area: Area of the circle describes the amount of space covered by the circle. So, it will give the coverage of circle as a two-dimensional plane.

### Diagram: Source: en.wikipedia.org

Where,

 r the radius of the circle. d the diameter of the circle. C circumference of the circle.

### Circle Formula:

1. The diameter of the Circle is computed as,

D = 2 × R

Where,

 D The diameter of a Circle R Radius of circle

1. Circumference of the circle is computed as,

C = 2 × $$\pi$$ × R

Where,

 C Circumference of circle R Radius of circle

1. Area of the circle is computed as,

A = $$\pi$$ × R2

Where,

 A Area of circle R Radius of circle

### Solved Examples on Circle Formula

Q. A circular ground has a diameter of 800 m. Calculate the area of the circle.

Solution:

First we have to find radius of the circle as,

R = $$\frac{D}{2}$$

i.e R = $$\frac{800}{2}$$

R = 400 m

Now,

Area of circular ground,

A = $$\pi$$ × R2

= $$\pi$$ × (400)2

=  $$\frac{22}{7}$$ × 400 × 400

= 502857.14 sq m

1. Find the area of the circle with length of circumference as 440 cm.

Solution:

First find the radius of the circle as,

C= 2 × $$\pi$$ × R

i.e. R = $$\frac{C}{2 × \(\pi$$}\)

= $$\frac{440}{2 × 7}{22}$$

= 70 cm

Now, find the area of the circle as,

A = $$\pi$$ × R × R

= \frac{22}{7} × 70 × 70

=15400 sq cm.

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