# What is the diameter of a circle whose area is 16pi?

Dec 25, 2015

$8$

#### Explanation:

Use the formula for the area of a circle:

$A = \pi {r}^{2}$

Here, the area is $16 \pi$:

$16 \pi = \pi {r}^{2}$

Divide both sides by $\pi$:

$16 = {r}^{2}$

Take the square root of both sides:

$\sqrt{16} = \sqrt{{r}^{2}}$

$4 = r$

Since the radius of the circle is $4$, the diameter is twice that:

$d = 4 \times 2 = 8$

Aug 8, 2018

$8$

#### Explanation:

Recall the formula for the area of a circle:

$A = \pi {r}^{2}$, with radius $r$

We see that our radius is $\sqrt{16}$, or $4$.

Recall that the diameter is twice the length of the radius, so we can multiply this by $2$ to get a diameter of $8$.

Hope this helps!