A circle measures 12 feet in diameter. What's its area to the nearest foot?

Square footage does not apply to circles. The flat area of a 12 ft circle is 37.69816992 (using the formula 12 x 3.14151416). If the circle is a container, then you can calculate volume in cubic feet or inches by multiplying the area x depth - but don't forget to convert feet to inches and/or inches to feet.