how can you find the circumference of a circle if you only know the area?
DESCRIPTION
How can you find the circumference of a circle if you only know the area?. For Example. A circle has an area 16 π cm 2 . What is the circumference of the circle?. In this lesson you will learn how to find the circumference of a circle by using the measure of area. Area of a Circle = π r 2. - PowerPoint PPT PresentationTRANSCRIPT
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How can you find the circumference of a circle if you only know the area?
For Example
A circle has an area 16πcm2. What is the circumference of the circle?
![Page 2: How can you find the circumference of a circle if you only know the area?](https://reader036.vdocuments.net/reader036/viewer/2022081507/56815b4d550346895dc9325f/html5/thumbnails/2.jpg)
In this lesson you will learn how to find the circumference
of a circle by using the measure of area.
![Page 3: How can you find the circumference of a circle if you only know the area?](https://reader036.vdocuments.net/reader036/viewer/2022081507/56815b4d550346895dc9325f/html5/thumbnails/3.jpg)
Let’s ReviewLet’s Review
Area of a Circle = πr2
Circumference of a Circle= πd or 2πr
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Let’s ReviewLet’s Review
The reverse of squaring a number is finding the square root.
32 = 9
= 3
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Let’s ReviewA Common Mistake
Finding the square root of a number is not the same as dividing it by 2.
Wrong
= 8
Correct
= 4
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Let’s ReviewCore Lesson
Bill has a circular garden that he wants to put a fence around. He knows that the area of a garden is 16π
yds2. How much fencing does Bill need to go around the circumference of the garden?
A = 16π yds2
A = πr2 C = 2πr
r2 = 16 yds2
r = 4 yds
4 yds C = 2π(4 yds)
C = 8π yds
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Let’s ReviewCore Lesson
A circle has an approximate area of 28.26 ft2. If 3.14 was used for pi, what is the circumference of the circle?
A = πr2
28.26 ft2 = 3.14r2
3.14 3.14
9 ft2 = r2
3 ft = r
C = 2πr
C = 2(3.14)3
C = 18.84 ft
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In this lesson you have learned how to find the circumference
of a circle by using the measure of the area.
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Let’s ReviewGuided Practice
A circle has an area of 25π cm2. What is the circumference of the circle?
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Let’s ReviewExtension Activities
The area of a circle is 16π meters2. Stephanie concluded that the circumference of the circle would be 16π. She stated “the radius would be 8 meters since the square root of 16 is 8.” What mistake did Stephanie make. Write an explanation describing how to fix her mistake.
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Let’s ReviewExtension Activities
A circle inside of a square touches the square at each edge as shown below. If the circle has an area of 25π feet2, find the area of the square.
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Let’s ReviewQuick Quiz
Find the circumference of the circle that has an area of 81π m2.
A circle has an area of 113.04 cm2. What is the circumference of the circle?