Friday, July 5, 2013

Circumference of a Circle


In this video you will learn
Equation to find the circumference of a circle
Equation for finding circumference using diameter
How to find circumference using the radius

Transcript

Hi Welcome to MooMooMath. Today we are going to look at how to find the circumference of a circle. Circumference has a formula and circumference is equal to d times pi (π =3.14) some people write two pi r. I prefer the d pi formula where d is the diameter of the circle and pi is 3.14 or slightly over three. So let’s work this example. We have a circle and we have a distance from the center of the circle to the side of the circle which is the radius and that is four. Now we know the diameter is the distance all the way across the circle so if I extend this all the way across is equal that is the diameter. I have two radiuses that create a diameter. Our diameter is eight, and then I will plug it into my formula.  So I take d which is 8 times π which is 3.14 and that equals 25.14 so my circumference is 25.12 now that is a linear measure. Now let’s look at the rules. The circumference is the distance around a circle. It is similar to the perimeter of a polygon. The two formulas you can use are d times π or 2 times the radius times π. Hope this was helpful.
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