Friday Fave for October 14

The Friday Fave is delighted to bring you a trio of activities this week, inspired by Stefan Fritz, and edited with a good deal of love by Desmos.

In Inequalities on the Number Line, we start simply and informally. Move the point to show a number less than three. Any number less than three is good, although we encourage students to pick a number that their classmates won’t.


We’re building towards asking them about all numbers that are less than three, of course. But the formalities of the symbolic and graphical representations of this idea can wait because we want to build on what they know. One number, then three numbers, then all of the numbers your classmates picked.


We build on this representation in order to introduce the shaded number line, and even the open dot for strict inequalities.


Another quality making this set of activities a fave is that students do many kinds of things in each activity. They plot points. They engage in card sorts. They interpret number line representations as inequalities. They look for similarities and differences among a set of inequalities.

These activities represent some of our best thinking about the interactions between students’ informal mathematical ideas and the formal representations they need to learn, and about using electronic tools to engage students in meaningful mathematical activity.

But don’t take the Friday Fave’s word for it. Here are links to the whole set:

Inequalities on the Number Line

Compound Inequalities on the Number Line

Absolute Value Inequalities on the Number Line