Name: Knowunity
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The formula to find circumference and area of circles. Also describes what area, circumference, radius and what diameter is.

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Study note

LUCY

United States of America

DEFAULT (US)

DEFAULT

Geometry

Arithmetic

Area and circumference of a circle 

Circles

Area and Circumference of Circles

Area and Circumference Notes
The radius of a circle is the distance from the center of a circle to any point on the circle. The
radius is half of the diameter.
radius
The distance across a circle through the center is called the diameter.
diameter
Circumference of a circle is simply the distance around the circle. The circumference is similar to
perimeter of a shape such as a rectangle.
Circumference formula:
С=2лr or ad
In this formula C stands for circumference, 2 is just the number 2, is for purposes of this class
equal to 3.14, and r is the radius of the circle.
The area of a circle is the number of square units inside that circle.
Area Formula:
А= πr²
A is area, is again "pi" or 3.14, r is radius and it is squared. Be careful to follow order of
operations when using this formula. The formula doesn't work if we multiply pi times r first and
then square that number. The squared sign applies ONLY to the radius.
or "pi"= 3.14 for all purposes during this class.
Example 1:
r = 4cm
C=2л4
C=2(3.14)(4)
C=25.12cm
А=π4²
A=3.14(16)
A=50.24 cm²
Example 2:
d = 10 cm
С=л10
C=(3.14)(10)
C=31.4cm
А=π5²
A=3.14(25)
A=78.5 cm²

Area and circumference of a circle

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Area and circumference of a circle

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Similar Content

Can't find what you're looking for? Explore other subjects.

Knowunity is the # 1 ranked education app in five European countries

Knowunity was a featured story by Apple and has consistently topped the app store charts within the education category in Germany, Italy, Poland, Switzerland and United Kingdom. Join Knowunity today and help millions of students around the world.

4.9+

20 M

#1

950 K+

Still not sure? Look at what your fellow peers are saying...

I love this app so much [...] I recommend Knowunity to everyone!!! I went from a C to an A with it :D

The application is very simple and well designed. So far I have found what I was looking for :D

Love this App ❤️, I use it basically all the time whenever I'm studying