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1978 AMC 12 Question 2

AMC12 · 1978 AMC 12

Question 2

If four times the reciprocal of the circumference of a circle equals the diameter of the circle, then the area of the circle is
  1. $\frac1{\pi^2}$
  2. $\frac1\pi$
  3. $1$
  4. $\pi$
  5. $\pi^2$