The Area of a Circle

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The Area of a Circle

• By Jodi Smith

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Susan has a swimming pool. She wants to know the
area of her pool. How can she figure this
problem out? What do we need to figure out the
area of a circle? Lets read on to find out
how to find the area of a circle!
r 3
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What is Area?

• Area is how much space an object
  takes up.
• We always label area units squared.
• Examples
• sq. ft
• sq. cm
• sq. m

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How to Find the Area of a Circle

• The area of a circle
• can be found by using
• something known as PI.
• PI 3.14
• The PI sign is

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What Else do You Need to Find the Area?

• Radius is half the diameter of a circle.
• Diameter is a line
• that cuts the circle
• in half.

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What Do We Do Next?

• First we need to take the radius of the circle
  and PI.
• What we have to do next is use our
  multiplication skills to finish the problem.
• But what is the formula for
• the area of a Circle??????

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The Formula For the Area of a Circle

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Now that we know the formula for the area of a
circle, we can find the answer. We know the
radius is 3. We know PI is 3.14 So.....we take 3
and square it. This will give us 9. Then multiply
by PI(3.14).
r 3
Our answer is 9 or 28.26 square units
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Whats the area of Susans swimming pool?

• Susan had a swimming pool with a radius of 3
  units.
• A r
• 3 units squared 9 units
• The area of her pool is
• 9 or 28.26 sq. units

r 3
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Helpful links for finding the area of a Circle

• http//www.mathgoodies.com/lessons/vol2/circle_are
  a.html