Area of a Circle: Finding Area based off Perimeter and Vice Versa

A circle has a circumference of

$10\pi$ cm. What is its area?

$25\pi$ cm²

A circle has an area of $36\pi$.
What is the circumference?

$12\pi$ cm

The circle below has a circumference of $8\pi a$ cm.

What is the area of the circle?

$16\pi a^2$ cm

A circle has a circumference of

$3\pi x$ cm.

What is its area?

$2.25\pi x^2$ cm²

A circle has a circumference of 6.28.

What is its area?

π

A circle has an area of $81a^2\pi$.

What is its circumference?

$18a\pi$ cm

A circle has an area of $\frac{\pi x^2}{4}$ cm².

What is its perimeter?

$\pi x$ cm