How to calculate the area of a circle.

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# How to calculate the area of a circle. - PowerPoint PPT Presentation

How to calculate the area of a circle. It’s as easy as pi. Let’s first make sure that we understand the difference between circumference and area. The circumference of a circle is the perimeter of the circle. Imagine that the circle is straightening itself out. The length of this line

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Presentation Transcript

### How to calculate the area of a circle.

It’s as easy as pi.

The length of this line

segment is the

circumference

of the

circle.

314 cm

Remember that the area of a rectangle is length x width because you’re calculating the total number of squares inside of the rectangle.

2

4

That’s fine and dandy, but a circle is not a polygon. It does not have straight sides; it has curves.
Believe it or not, this is really our “friend” the parallelogram. And, we know how to calculate the area of a parallelogram.
To find the area of the circle (which is now a parallelogram), we just need to multiply the Base by the Height.

Height

Base

Wait a minute! The height of this “parallelogram” is really the radius of the circle.

Base

10 x 10 x 3.14 = 314 cm2

Make sure that you use the radius of the circle.

20 cm

7 x 7 x 3.14 = 153.86 cm2

Make sure that you use the radius of the circle.

14 cm