math

The area of circle c is 81 pi . if the radius of the circle is doubled, what is the circumference of the new circle ?

please answer and explain

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asked by Thomas
  1. 162 pi

  2. my answer is 162 pi too, but the answer is

    a. 18 pi
    b. 36 pi
    c. 36 pi^2
    d. 324 pi
    e. 324 pi^2

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    posted by Thomas
  3. if a = 81pi, r = 9
    if r = 18, c = 36pi

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    posted by Steve

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