The Circumference of a Circle is the distance around it. That is, the circumference would be the length of the circle if it were opened up and straightened out to a line segment. The word circumference is used when we are measuring physical objects, as well as when considering abstract geometric forms.
The circumference of a circle is related to one of the most important mathematical constants. This constant, pi, is represented by the Greek letter π. Pi is defined as the ratio of a circle’s circumference C to its diameter d.
It is denoted as:
or C= 2π.r
We will show you examples you both formulas.
1. Find the circumference of a circle with a radius of 3 cm.
First, we need to find the diameter. The diameter is twice the radius, so 2 x 3 cm = 6 cm
C = π.d = 6 π
C = 6 x 3.14
C = 18.84 cm or 6 π
2. You are cutting out a paper to wrap around the edge of a cake you have just baked. The radius of the pie is 5 inches.
C = 2πr
C = 2π x 5
C = 10π
C = 31.4 inches