Multiple choice

If C is the circumference of a circular disk in centimeters and A is the area of the same circular disk in square centimeter Then $\displaystyle \frac{C}{A}=\frac{A}{C}$ iff r =

  1. $1$
  2. $2$
  3. $3$
  4. $4$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

C = 2*pi*r, A = pi*r^2. C/A = (2*pi*r) / (pi*r^2) = 2/r. A/C = (pi*r^2) / (2*pi*r) = r/2. 2/r = r/2 implies r^2 = 4, so r = 2.

AI explanation

The circumference formula is C equals 2 pi r and the area formula is A equals pi r squared. If C divided by A equals A divided by C, then C squared equals A squared, so C equals A. Setting 2 pi r equal to pi r squared and solving for the radius gives r equals 2.

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