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Circumference, Area,
Surface Area, and Volume
By Taylor Winter
Sue baked a pie for her friends. She knows that the circumference of the pie is 24π inches. She wants to know how long will one piece of pie be?
The radius of a circle is 4 meters. What is the circumference?
Derive the Formula:
Circumference of a Circle
Example Problems
1. We know that C/D=π is always true.
2.If you times each side by D we get C=π x D.
3. We know that D = 2 x R
4. We can substitute D with 2R and get the formula 2 x π x R or 2πR.
Definition of Circumference
The circumference means the distance around a circle
C= Circumference D= Diameter R= Radius
We are given the information that R= 4 meters.
Using our formula of 2πR we can substitute 4 meters for R.
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2π4m
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Now we multiply.
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Exact answer is 8π meters or about 25.12 meters.
We are given that C=24π inches
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Using our formula C=2πR we can substitute C for 24π.
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24π inches =2πR
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We know that one slice of pie will be equal to the length of R.
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Divide each side by 2π of get R alone.
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24π inches/2π = 2πR/2π
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We are left with 12 inches = R.
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One slice of pie will be 12 inches long.
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