So Happy Together #6

The Oakland presentation is behind me but the value of this digital projector becomes more apparent every day. This digital projector is decreasingly an affectation and is increasingly essential to my math practice.

Here is a Vimeo clip [1:14] I edited to illustrate what is no doubt some well-known cognitive theory which I’ve been too lazy to study, but which I arrived at through two years of error and trial and error just the same.

So Happy Together #6 from Dan Meyer on Vimeo.

In summary: as you’re scaffolding a complicated task, it’s essential to highlight the small differences, the subtle ways an easy problem — one which we’ve mastered — now becomes difficult. The brain senses differences and a digital projector makes those differences more apparent than does a) a pencil and paper, b) your voice, or c) a whiteboard and dry-erase marker.

I'm Dan and this is my blog. I'm a former high school math teacher and current head of teaching at Desmos. He / him. More here.


  1. I use a projector everyday in my history classes.

    My math classes I still need to think about. I can use it to show the contents of a lesson, but I have no way to actively do problems on it. Any suggestions?

  2. bcarrera — Make a “poor woman’s smart board” by projecting directly on your white (or in my case green-chalk) board.

    You can still write on your original board. Over the image. Nifty, huh?

    And the eraser works to … um … erase.

    My students are past being impressed by technology and don’t even notice the difference between a static image being presented by data projector or printed on an overhead transparency and being projected that way.

    And the kids LOVE to use chalk/markers and write over a projected image. That is a novelty to them.

  3. One thought Dan, would it be easier for the cherubs to follow if the next slide instead showed a strikethrough of the y-intercept and listed the coordinates of the point below?

  4. Only a matter of time before schools catch on and start replacing overhead projectors, dry erase markers, overhead slides, and other consumable presentation materials with digital projectors. Especially as the content we deliver becomes and and more visual and digital in nature.