Here is a problem I have been working on this afternoon. I worked on building a model in Geogebra to help students understand the situation.

**2013 Probe I Problem #3**

A cylindrical can with radius of 6 inches is filled with 2 inches of water. When a smaller cylindrical can 4 inches tall is placed inside of the first with its bottom lying on the bottom of the first, the water in the first can rises a further inch to 3 inches. What is the radius of the smaller can?

**A. 3 B. sqrt(12) C. sqrt(15) D. 4 E. sqrt(18)**

Here is a screenshot of the Geogebra model I constructed.

Here's a PDF of my typed-up solution.

Here's the Geogebra Sheet (built in the Geogebra 5.0 beta with 3-D graphing) if you'd like to take a look.