The formula for the area of a circle is

We know the diameter, and the radius is half of the diameter. So the radius is 9. Now we plug that into the formula.

So the answer is B, 81 pi square feet
If the three integers are
, then we have

We can combine the fractions on the left side:


That is true that microwave ovens cause friction to water molecules
It has a surface area to volume ratio of 1:1