I don't know how many elementary school teachers use Geogebra in their classrooms, but I suspect it's probably not many. Yesterday I led a follow-up workshop session for a group of mostly K-5 math teachers. I showed how to use Geogebra to make a number line with tick marks noting common fractions.

A thought experiment: suppose you are a K-5 math teacher and want to show students how to compare the fractions 4/9 an 3/7 on a number line. The decimal expansions show these two values are pretty close to one another. 3/7 is approximately 0.428571 and 4/9 is approximately 0.444444. Drawing these two fractions on a number bounded between 0 and 1 might be tough. They may even appear to be the same if the scale isn't discerning enough. What would a person do to find number lines to make teaching materials? Like many people, he or she might go to Google and do something like this:

We may able to find number lines with sevenths and ninths indicated, but they will probably be separate. It may take some time to dig through these images. * Should a teacher be at the mercy of materials made by somebody else? What if the teacher could design his or her own materials instead? *Enter Geogebra.

Here's a PDF I made with some basic instructions on how to start building number lines: Creating Number Lines with Fractions in Geogebra

In addition to a PDF showing an introduction on how to make these things, I also posted a Geogebra sheet on the Geogebra community site for teachers to download for free. An image of the sheet I built appears below.