Assuming the glass is a cylinder, the volume is equal to the area of the base (pi x radius2) multiplied by the height of the cylinder. More specifically:
Volume = pi x radius2 x height = pi x (2)2 x 3 cubic inches
The volume of the glass (in cubic inches) is how many cubic inches of water (or any other substance) the glass can hold.
If you don't know, "pi" is a very special number, called a transcendental number. It is equal to the ratio of a circle's circumference to it's diameter, which is approximately 3.141592654. In fact, the digits of pi go on forever without repeating themselves in any known pattern, which means pi is also what is known as an irrational number. It appears in many places in math and other sciences, and has been known about and studied for thousands of years. You often see pi approximated to 3.14, or sometimes 22/7.
Hope this helps!
We need to assume a few things to answer this question.
First: we need to assume that the glass is straight up and down (the radius doesn't change).
Second: we need to assume that we want to fill the glass right to the brim.
Then we can use the formula for a cylinder;
Volume = Pi(r)2 x height
Hope this helps,