4
Votes

What is the equation for circumference of a circle?

By Ryan McGuire on the 10th of January, 2013

10 Answers

  • 1
    Vote

    Circumference equation is =2 x (Pie) x (R)

    Wher Pie =3.1417

    R-Radius of Circle

    Refine By AMRITA CHAKRAVARTY on the 21st of January, 2013

  • 1
    Vote

    The circumfrance of a circle can be found out using the equation   C= 2Pir.      Where r is the radius of the circle, and Pi has a value of 3.14.

    Refine By Adersh Antony on the 19th of January, 2013

  • 1
    Vote

    Circumference is the measurement surrounding around a circle using the "middle" of a circle.

    To find the circumference you need to use one of  the following formulas. First you have to find out what information you are given or can measure. Depending on the information you have, you may need to calculate the diameter of the circle before you can find the circumference. If you are only given a radius, you will either need to calculate the diameter or use a different formula.

    (A VIDEO explaining this can be found here: "http://video.about.com/math/How-to-Calculate-Circumference.htm")

    Circumference of a circle:

     

    Circumference = π × diameter

    Circumference = π × 2 × radius

    Pi = π = 3.14159265359...

    Pi

     

     

     

     

     

    Refine By Dawn Lubka on the 15th of January, 2013

  • 1
    Vote

    In circles the circumference is 3.14 (p) times the Diameter.

    Thus the formula looks like:
    Area= pd.

    And since diameter(d) is 2 times radius(r) i.e. d=2r

    Area= pd=2pr

    Refine By Parvathy Neelakantan on the 16th of January, 2013

  • 1
    Vote

    The distance around a circle is called the circumference. The distance across a circle through the center is called the diameter. Pi is the ratio of the circumference of a circle to the diameter. Thus, for any circle, if you divide the circumference by the diameter, you get a value close to Pi. This relationship is expressed in the following formula:

    C over d equals Pi

    Refine By Bridget Gaskin on the 17th of January, 2013

  • 0
    Vote

    The equation for thecircumference of a cicle is 2Pir

    where the value of Pi =3.142

    and r is the radius of the circle i.e length of a straight line drawn from the centre of the circle to its circumference.

    Refine By pranit on the 17th of January, 2013

  • 0
    Vote
    The distance around a circle is called the circumference. The distance across a circle through the center is called the diameter. Pi is the ratio of the circumference of a circle to the diameter. Thus, for any circle, if you divide the circumference by the diameter, you get a value close to Pi. This relationship is expressed in the following formula: [IMAGE]
    C over d equals Pi

    Refine By Bridget Gaskin on the 17th of January, 2013

  • 0
    Vote

    The circumference of a circle can be calculated from its diameter using the formula: Circumference of a circle = 2*pi*radius

    Refine By jagadish on the 14th of January, 2013

  • 0
    Vote

    First measure the diameter (the width) of the circle.

    Then times it by Pi (or just 3.142)

    So if the diameter of a circle is 10 cm across the circumference would be 31.42 cm

    Refine By henry warren on the 14th of January, 2013

  • -2
    Vote

    The 

    Refine By pranit on the 17th of January, 2013

Suggested reading…

Calculate the area of a circle

How to calculate the area of a Circle: C=πr2

But what does this mean?

Some facts you might need to know first:

circle is a shape where every point on its edge is the same distance from the centre. 

The distance from the centre to the edge of the circle is called the Radius.

The distance from one side of the circle to the other, going through the centre, is called the Diameter. This is also double the length of the Radius.

π (pronounced Pi) is a special number that is calculated by dividing the circumference of a circle by the diameter. No matter what size circle you have, this number always stays the same. In reality, this number is never ending, but we can approximate it to 3.14, but to make it easier for us, since this number never changes, we just call it Pi and write it π. 

The Area of a circle

C = circumference
d = diameter
r = radius

The formula for an area circle, if you know its radius, is given by:

A= π r2

 

Area of a Cirlce

 

But what if you know the diameter?

You can either divide the diameter by 2 which gives you the radius and then use the formula above or use:

A=(1/4) x πd2

Remember, the area of a circle is given in square units! (e.g cm2)

 

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