Below are a bunch of screen movies plus an essay about interpreting the model. Most of the screen movies are based on this spreadsheet, which I made quite a long time ago and then forgot about it. I was delighted to find I'd done it and then made the movies to explain how it can be used. The first worksheet is like one of those old paper based workbooks that used to accompany introductory textbooks - there are cells for the students to fill out. In this case, the students get immediate feedback whether they have done this correctly or not. The worksheet also treats the budgeting exercise in integer form. This should make things more transparent for the student. Fractions and a continuous approach to budget are introduced in the third and subsequent spreadsheets. After the movies about the spreadsheet there are a couple of very short movies done in digital ink, akin to the old chalkboard type of presentation. Hopefully it is transparent how to move from the spreadsheet approach to the hand written approach.
Each movie is captioned and the Transcripts are available for view as well. I've noticed some tiny errors in the transcripts that I've not gone back to correct. Perhaps I should have the students crowd source the correction of these errors. That is something to explore further.