What is the area of a circle with diameter 34mm?
Half it to find the radius and then use the formula
The formula for the area of a circle is
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
Now we simply substitue in our value for
So if you want an exact value the answer is
The area of a circle is given by the formula