# What is the area of a circle with diameter 34mm?

Nov 10, 2015

Half it to find the radius and then use the formula $A = \pi {r}^{2}$ to find the area.

#### Explanation:

The formula for the area of a circle is $A = \pi {r}^{2}$ where $A$ is the area and $r$ is the radius.

Since we only know the diameter we need to figure out the radius. Since the radius is always half the diameter we now know that the radius is 17mm and that means we know that $r = 17$

Now we simply substitue in our value for $r$ into the formula.

$A = \pi {17}^{2}$
$A = 289 \pi$
$A = 907.92 m {m}^{2}$ (To two decimal places)

So if you want an exact value the answer is $289 \pi m {m}^{2}$ or if you want a decimal answer then it is $907.92 m {m}^{2}$ or $9.0792 c {m}^{2}$

Nov 10, 2015

$907.9 m {m}^{2}$

#### Explanation:

The area of a circle is given by the formula $\pi {r}^{2}$, and the diameter is twice the radius of the circle. Knowing this, we can see that:
$A = \pi \times {\left(\frac{34}{2}\right)}^{2}$

and thus

$A = \pi \times {17}^{2} = 907.9 m {m}^{2}$