Question

If the area of a circle measures 9π cm2, what is the circumference of the circle in terms of π?

Answer 1

Answer: option B

Step-by-step explanation:

The circumference of a circle can be calculated with this formula:

$C=2\pi r$

Where "C" is the circumference of the circle and "r" is the radius of the circle.

The area of a circle can be calculated with:

$A=\pi r^2$

Where "r" is the radius.

Knowing the area, you can solve for the radius:

$r^2=\frac{9\pi cm^2}{\pi }\\\\r=\sqrt{\frac{9\pi cm^2}{\pi } }\\\\r=3cm$

Substituting into  $C=2\pi r$, you get that the circumference of this circle is:

 $C=2\pi (3cm)=6\pi\ cm$

Answer 2

Answer:

B

Step-by-step explanation:

The area (A) of a circle = πr² ← r is the radius

here A = 9π, hence

πr² = 9π ( divide both sides by π )

r² = $\frac{9\pi }{\pi }$ = 9

r = $\sqrt{9}$ = 3

The circumference (C) of a circle is C = 2πr, hence

C = 2π × 3 = 6π → B