In previous posts, I’ve presented fraction-related Web Sketchpad models from the Dynamic Number project.  Several of these activities—specifically Dividing and Subdividing and Deducing the Mystery Fraction —focus on a number-line representation of fractions. Below (and here) is another such websketch, with students constructing segments of fractional length that can be placed end to end to add them together.

As with the prior fraction models, a nice feature of the fraction tool showcased here is the ease and accuracy of building any fraction you like. The video below the websketch explains how to use the interactive model and offers several suggestions for fraction-related explorations.