Here's another in a growing list of interactive tools which is designed more or less with no set of questions or planned activities in mind—just a modeling tool, from which you may be able to generate your own questions. This tool is available in the free Grade 7 Introduction to Proportions lesson app.

Enter ratios and observe how they are modeled. How is each ratio generated? How does the model change to represent the ratio you enter? Here are some more questions:

- How can you tell if they're greater than 1 : 1? less than 1 : 1? equal to 1 : 1?
- Given different starting ratios, what effect does changing the numerator have on the model?
- What effect does changing the denominator have? What makes these changes work?
- Why are these models NOT fraction models?
- Set up different ratios. Do they form a proportion? How do the models tell you this?

You can also set up different non-equivalent ratios. Then ask students to change one number so that the ratios form a proportion. How many different ways are there to do this?