How Many Square Inches In 12 Inch Diameter Circle?

The formula for the area (A) of a circle is A = πr² but this can also be stated as πd²/4 where r and d are the radius and diameter respectively.
A = πd²/4 = π x 12²/4 = π x 144/4 = π x 36 = 113.097 square inches.

One of you has the correct formula but the wrong answer.
Radius squared times Pie.  6x6xPie = 113.1 (or
dia. Squared times Pie div. 4.   12x12xPie : 4 = 113.1)

126 inches