Question

The circumference of a circle is $30\pi$. What is its area?

• A. $15\pi$
• B. $225\pi$
• C. $400\pi$
• D. $900\pi$

Answer 1

The correct option is B $225\pi$

The circumference of a circle is given by the formula $2$$\pi r$, where $r$ is the radius of the circle. Substitute the given circumference into this formula and solve for $r$.
$30\pi$= $2\pi r$.
Therefore, the radius of the circle is $15$. Use this to find the area of the circle. The area of a circle is given by the formula $A=\pi r^2$. Substitute the length of the radius into this formula and calculate the area.
$A=\pi (15{)}^2=225\pi$