Etch-A-Sketch and Lite Brite

The classic red-and-white Etch A Sketch model
Image via Wikipedia

This has worked wonders in my algebra 2 classes when we’re discussing ways to write domain and range. Talking about a continuous graph, I’ll describe it as an Etch-A-Sketch graph. When I reference a discrete graph, or as they know it – a collection of ordered pairs-I call it a Lite Brite graph. Kids get it.

When we’re looking at an Etch-A-Sketch graph, we know to usually describe the domain with inequality symbols, whereas with a Lite Brite graph every element (or brite peg) must be listed.

This is even useful for discussing whether or not the graphs (relations) are functions or not. Most cool pictures on either display will obviously not be functions however.  This year I asked for a student volunteer to draw a function on the Etch-A-Sketch while it sits under the document camera. It’s hilarious because if the student turns only the right knob, game over. That’s the vertical knob. It takes a mixture of x and y components, or turning both knobs, to avoid the buzzer that accompanies an undefined slope.

Lite Brite Snail

Image by J.G. Park via Flickr

Keeping a Lite Brite and an Etch-A-Sketch in my classroom makes my teaching better and usually brings back positive childhood memories for me and my students. It’s a win-win.