How many square inches are in a 16 inch diameter circle?

To do this, you first find the radius of the circle. To do this, you divide 16 by pi, which gives 5.09 (to two decimal places). Half of this gives you the radius - around 2.55. You then square the radius, in this case giving approximately 6.48, and multiply it by two, which yields the answer of roughly 12.97. There's your answer - 12.97 inches squared (to two decimal places).

N.B. These averages may seem slightly off, but I did the calculations on a calculator, simplifying each step.