How to Find the Diameter if You Know the Circumference

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Whether you're solving a math problem for school, making crafts, or putting fencing around your thou, knowing how to summate the circumference of a circle volition come in handy in a diversity of circle-related problems. Nosotros'll teach you the central circumference formulas you need to figure out the circumference of a circle when you know either the diameter or radius.

  1. 1

    Use the formula C = πd to detect the circumference if yous know the diameter. In this equation, "C" represents the circumference of the circumvolve, and "d" represents its diameter. That is to say, you can find the circumference of a circle just by multiplying the diameter by pi. Plugging π into your computer will give you its numerical value, which is a closer approximation of iii.14 or 22/7.[1]

    • Bore means a straight line segment that passes through the center of the circle and has its endpoints on the sides of the circle.
  2. 2

    Plug the given value of the diameter into the formula and solve. Check out the example trouble below if you lot'd like extra practice.[2]

    • Example problem: You have a circle tub with a diameter of viii feet, and y'all desire to build a white argue that creates a six-foot wide infinite around the tub.
    • To find the circumference of the debate that has to be created, you should beginning discover the diameter of the tub and the argue which will be eight anxiety + 6 feet + vi feet, which volition account for the entire diameter of the tub, plus the infinite betwixt the tub and fence.
    • The diameter for your circular fence is 8 + 6 + 6, or 20 feet. Now plug it into the formula, plug π into your calculator for its numerical value, and solve for the circumference:
    • C = πd
    • C = π 10 20
    • C = 62.eight feet

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  1. 1

    Use the formula C = 2πr to notice the circumference using the radius. In this formula, "r" represents the radius of the circle. Again, you can plug π into your calculator to get its numeral value, which is a closer approximation of 3.14.[iii]

    • A radius is any line segment that extends from the center of the circle and has its other endpoint on the edge of the circle.
    • You lot might notice this is like to the C = πd formula. That'due south because the radius is half as long every bit the diameter, and then the bore can be thought of equally 2r.
  2. 2

    Plug the given radius into the equation and solve. For this example, let's say you're cut out a decorative strip of newspaper to wrap around the border of a pie yous've only made. The radius of the pie is five inches. To find the circumference that you need, just plug the radius into the equation:[iv]

    • C = 2πr
    • C = 2π ten 5
    • C = 10π
    • C = 31.four inches

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C = 2π r

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  • Question

    What is the perimeter of a circumvolve?

    wikiHow Staff Editor

    This answer was written by one of our trained team of researchers who validated it for accuracy and comprehensiveness.

    wikiHow Staff Editor

    wikiHow Staff Editor

    Staff Answer

    The perimeter of a circle is the same equally its circumference, the altitude around it. The term "perimeter" refers to the altitude around whatever airtight shape, and "circumference" applies specifically to a circumvolve or arc.

  • Question

    What'due south the difference between the circumference and the diameter?

    wikiHow Staff Editor

    This answer was written by i of our trained team of researchers who validated it for accurateness and comprehensiveness.

    wikiHow Staff Editor

    wikiHow Staff Editor

    Staff Answer

    The diameter is the length of a straight line drawn through the heart of a circle from 1 side to the other. The circumference is the length all the way effectually the outside of the circumvolve.

  • Question

    What is a circumference?

    Community Answer

    Circumference is the altitude around the perimeter of a circle. Information technology is calculated by multiplying the distance beyond the middle (diameter) by Pi (3.1416).

  • Question

    If I know the radius of a circle, how I tin find the circumference?

    Donagan

    Double the radius to get the diameter. Then multiply by pi to get the circumference.

  • Question

    How do I discover the radius when I go the circumference?

    Community Answer

    The circumference = π x the diameter of the circumvolve (Pi multiplied by the diameter of the circle). Only carve up the circumference past π and yous volition have the length of the diameter. The diameter is just the radius times two, so divide the bore past ii and you volition have the radius of the circle!

  • Question

    How can I find the bore of the circumvolve, once I know the circumference?

    Community Answer

    Circumference (C) = pi * diameter(d). To become the diameter of a circumvolve have the circumference (C) and dissever it by pi (three.14).

  • Question

    How do I detect the surface area of a circumvolve when just given the circumference?

    Donagan

    Separate the circumference by pi. That's the diameter. Split up by 2. That's the radius. Square the radius, and multiply by pi. That's the expanse.

  • Question

    What is the formula used to calculate bore?

    Community Answer

    The diameter is twice the radius. The circumference is diameter 10 pi, or 2 x radius x pi.

  • Question

    How do I change the mixed number into radius?

    Community Answer

    If your radius is a mixed number, turn the number into an improper fraction. To do this, just multiply the whole number part by the denominator and add that number to the numerator. The denominator should remain the same throughout the process. You tin and so apply the improper fraction in your formula.

  • Question

    What is the answer of the circumference of a circle?

    Community Answer

    The answer depends on your number. For example, pie or iii.14 is multiplied with your number which is the diameter or radius.

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VideoRead Video Transcript

  • Consider buying a scientific or graphing calculator that already has π as ane of the buttons. This will mean less typing for you and a more accurate answer because the π push produces an approximation to π that is much more than accurate than 3.xiv.

  • Remember: some worksheets will ask to replace pi with a subside, such as 3.fourteen or 22/vii.

  • To find circumference from the diameter, merely multiply pi past the diameter.

  • The radius is always going to be half of the diameter.[5]

Thanks for submitting a tip for review!

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  • Accept your time. Call back the erstwhile aphorism—measure twice, cut one time.

  • If yous are stuck, inquire a friend, family member, or instructor for help.

  • Retrieve to always double-cheque your work because one mistake will prepare off all your data.

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Article Summary Ten

To calculate the circumference of a circle, employ the formula C = πd, where "C" is the circumference, "d" is the diameter, and π is 3.fourteen. If you take the radius instead of the diameter, multiply it by 2 to get the diameter. You can also use the formula for circumference of a circle using radius, which is C = 2πr. To see actual examples of the circumference of a circumvolve being calculated, read the article!

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Source: https://www.wikihow.com/Calculate-the-Circumference-of-a-Circle

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