The formula for the circumference of a circle is given by 2 * pi * r, where r is the radius. If the circumference is 9.42 inches, then we can write the equation:
9.42 = 2 * pi * r
Solving for r, we get:
r = 9.42 / (2 * pi)
The diameter of the circle is equal to 2 * r, so:
d = 2 * r = 2 * (9.42 / (2 * pi)) = 9.42 / pi
So, the radius of the circular donut is approximately 3 inches, and the diameter is approximately 9.42 inches.