Finding the circumference of a circle: formula and tasks

In this publication, we will look at how you can calculate the length / perimeter of a circle (circle) and analyze examples of solving problems.

Content

Length / Perimeter Formula

1. Through the radius 

The perimeter of a circle or the circumference (C) is equal to twice the product of its radius and the number π:

C = 2 * π *r

Finding the circumference of a circle: formula and tasks

Radius (r) is a line segment that connects the center of the circle and any point on it.

2. Through diameter

The perimeter / circumference of a circle is calculated as the product of its diameter by the number π:

C = π * D

Finding the circumference of a circle: formula and tasks

Diameter (d) is equal to two radii (d=2r). It is a line segment that connects two opposite points on a circle.

Note: in calculations the value of the number π rounded up to 3,14.

Examples of tasks

Task 1

Find the circumference of a circle if its radius is 12 cm.

Decision:

Let’s use the first formula, which involves the value of the radius: C u2d 3,14 * 12 * 75,36 cm uXNUMXd XNUMX cm.

Task 2

Find the perimeter of a circle if its diameter is 15 cm.

Decision:

Let’s apply the formula that uses the diameter: C = 3,14 * 15 cm = 47,1 cm.

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