Gemini 3 Pro gives me this:

> Based on the information provided, it is impossible to determine the inner diameter of the glass.

Here is why:

The Coaster Dimension: Knowing the coaster has a diameter of 9 only tells us the size of the object under the glass. It does not mean the glass is the same size; the glass could be smaller (fitting entirely on the coaster) or larger (overhanging the coaster). The Glass Dimensions: While you provided the wall thickness (1), you did not provide the outer diameter of the glass. To find the inner diameter, the formula is: Inner Diameter = Outer Diameter - (2 × Wall Thickness)

Without knowing the Outer Diameter of the glass, the calculation cannot be completed.