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