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Diameter is 7/22 cm. What is the circumference?

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enginr eNotes educator | Certified Educator

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We are given a diameter of 7/22 centimeters.

A diameter is the length of a straight line segment which passes through the center of a circle and has its endpoints on the circle itself.

The circumference of a circle is simply the length of one complete revolution of the circle.

The circumference of a circle is equal to the diameter (D) times pi (`D*pi` ). The circumference of a circle is also often stated as `2*pi*R`  where R is the radius. However, the diameter is simply twice the length of the radius, so we can see the two statements for circumference are equivalent.

`2*R=D` thus

`2*R*pi=D*pi`

So the circumference of our circle is:

`D*pi=(7/22)*pi=0.999 ` centimeters

Recall that the definition of pi is the circumference of a circle divided by its diameter. 

Pi = circumference / diameter = approximately 3.14

 

 

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misssilvestri | Student

We know that the formula for circumference of a circle is `C=2pir or`

`C=D*pi`

  • The diameter of a circle is the distance from one point on the circle, to another point on the circle passing through the center of the circle.
  • The radius is the distance between any point on the circle to the center of the circle.
  • From this information we can conclude that the radius is half the distance of the diameter. 

If you are given that the diameter is 7/22, then half of that would be 7/44.

Radius - 7/44.

You can use either formula with the given information. Using  `c=2pir`

  • Plug in the radius - 7/44.
  • `c=2pi7/44`
  • Remember that when multiplying fractions, we multiply the numerators and multiply the denominators. `2*7/44`
  •  Simply when necessary. Multiply across and simplify to `c=7/22picm`
  • Remember that when the problem gives specific units you must include them in your answer. You could also use the diameter formula. Your final answer should show that the circumference is `c=7/22pi`
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