The sides of a aquare field are 12 meters. A sprinkler in the center of the field sprays a circular area with a diameter that corresponds to a side of the field. How much of the field is not reached by the sprinkler?

The answer would be 31, because the area of the square would be 144 (12 x 12 = 144; A=S^2). You would then find the area of the circle (6^2 x pi = 113; A=pi x r^2). You then take the area of the square and subtract it with the area of the circle (144-113=31)