circumference circle

In our real life, we could see many circular objects. For example, wheel of a vehicle, shape of a pizza, tennikoit ring,.. Take a rope or an inelastic thread and measure the circular path of the given object and that forms the circumference of the circular object. As the size of the circle increases, the circumference of circle also increases.

Introduction on circumference of a circle:

Circle is one of the most important shapes in geometry. Circumference is defined as the measure needed to make the closed curve. Circle has a fixed center. Distance between the center and a point on the circumference of the circle is called as radius. A line passing through center and any two points on the circumference of the circle is called as diameter.  If the radius or diameter is given then we can easily calculate the circumference of the circle. This article helps us to find the circumference of the circle with the given details.


Circumference of a circle:


The diagram below shows the circumference of circle.



The Circumference of a circle can be calculated using the following formula:

Circumference = 2  `pi`r  or `pi`

where r ----> radius of circle

d ----> diameter of circle

π---- > constant and value of π is  3.14 or 22/7

Diameter is twice the radius. So d = 2r and   r = `d/2`


Problems on finding circumference of the circle:

Ex 1: Find the Circumference of the circle with radius 20 cm.

Sol:

Step 1: Write the formula

Circumference of a circle  = 2  `pi`r units

Step 2: Plug the known values and calculate circumference

2π r               = 2 (22/7) 20

= 2 (3.14) 20

= 125.6 cm

Ex 2: Find the Circumference of the circle with radius 32 cm.

Sol:

Step 1: Formula for Circumference of a Circle

Circumference of a circle  = 2  `pi`r units

Step 2: Plug the known values and calculate circumference

2πr                  = 2 (22/7) 32

= 2 (3.14) 32

= 200.96 cm

Ex 3: Find the Circumference of the circle with diameter 52 in.

Sol:

Step 1: Write the formula

Circumference of a circle  = `pi` d

Step 2: Plug the known values and calculate circumference

πd             = (22/7) 52

= (3.14) 52

= 163.28 in

Ex 4: Find the Circumference of the circle with diameter 74 in.

Sol:

Step 1: Write the formula

Circumference of a circle  = `pi` d

Step 2: Plug the known values and calculate circumference

πd            = (22/7) 74

= (3.14) 74

= 232.36 in

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Practice problems on circumference of the circle:


Find the Circumference of the circle with radius 18 cm. .
Answer: 113.04 cm

Find the Circumference of the circle with radius 28 cm.
Answer: 175.84 cm

Find the Circumference of the circle with diameter 63 in.
Answer: 197.82 in

Find the Circumference of the circle with diameter 81 in.
Answer: 254.34 in