Equation for Circumference of a Circle

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We can say circumference of the circle is the actual length around the circle. We have an equation or formula to find the circumference of the circle, that is 2 x π x r. Here r is the radius of the circle. And we know the value of the π that is 3.14 or22/7.

Example 1: Find the circumference of the circle with radius 21 cm.

Solution: From the problem we can write,

Radius = r = 21 cm

We know the formula to find the Circumference of the circle

That is C = 2 x π x r

Now we can plug the value in this formula, then we can write

Circumference of the circle=C = 2 x π x r

From this we can write

C = 2 x π x r = 2 x 22/7 x 21 = 132 cubic cm.

Example 2: Find the circumference of the circle with diameter 28 cm.

Solution: From the problem we can write,

Diameter = d = 28 cm

Radius =diameter/2 = 14 cm

We know the formula to find the Circumference of the circle

That is C = 2 x π x r

Now we can plug the value in this formula, then we can write

Circumference of the circle=C = 2 x π x r

From this we can write

C = 2 x π x r = 2 x 22/7  x 14 = 4 x 22 = 88 cubic cm.
 

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