   SEARCH HOME Math Central Quandaries & Queries  Subject: Cubic inches Name: Renee Who are you: Parent A glass has a height of 3 inches and a radius of 2 inches. about how many cubic inches of water will the glass hold? and how do you figure the answer? thank you 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!

Gabriel Potter

--

Hi Renee

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,
Melanie     Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences.