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Formula for Circumference of Circle (Perimeter) – Examples

Here you will learn what is the formula for circumference of circle (perimeter of circle) with examples.

Let’s begin –

What is Circumference ?

The perimeter (boundary) of a circle is called its circumference. It is the distance covered by travelling once around circle.

Formula for Circumference of Circle (Perimeter of Circle)

Circumference of circle = 2πr 

where r is the radius of circle.circumference of circle

And π is an irrational number whose approximate value is 227 or 3.1415….. unless specified, the value of π should be taken as 227

Circumference (Perimeter) of Semicircle

Perimeter of Semicircle = πr + 2r = r(π+2)

Rotating Wheels

(i) Distance moved by a wheel in 1 rotation = circumference of the wheel

(ii) Number of rotations in 1 minute = distance moved in 1 minute/circumference.

Example : Find the circumference of the wheel of cycle’s whose diameter is 21 cm.

Solution : We have, Diameter = 21 cm 

   Radius = 212  = 10.5 cm

Circumference = 2πr  = 2×227×10.5 = 66 cm

Hence, the circumference of wheel of cycle is 66 cm

Example : If the diameter of a semi-circular plot is 14 m, then find its perimeter.

Solution : A semi-circle has been drawn with AB = 14 m as diameter.

  Its radius,     r = d2 = 142 = 7 m

   Perimeter of semi-circle of radius 7 m = πr + 2r  = 227×7 + 2×7 = 36 m

Hence, the required perimeter is 36 m.

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