I spent some time this week browsing conference proceedings from ICTCM and AMATYC to try to find something to learn. As usual some of the sessions posted were things I already knew. Other sessions were things I didn’t want to learn. One that caught my attention was Workshop 14 at AMATYC’s 2009 conference. Rob Kimball presented It Is a Sure Bet. The Appropriate Use of Technology Deepens Understanding. (The link opens a spreadsheet).

Kimball’s session showed how to use spreadsheets in algebra classes at various levels. This is not surprising because he also led a reform project to find real-world problems in College Algebra called The Right Stuff.

I already knew how to do many things he does in this spreadsheet. For instance I have used sliders. Still, it is good to know that if I ever need a refresher on how to create sliders you can find it here. Kimball also has a creative version of the problem that is usually set up as delivery of utilities to a manufacturing plant or city on the other side of a river. In the traditional problem overland cables cost less to run than underwater cables, His set up instead involves creating an irrigation system on a large farm.

One simulation lets you vary the number of dice you use. To do this a simple if statement is used to turn on or turn off dice depending on a users preference. I also learned about the countif statement. Kimball uses this to count the number of virtual dice showing sixes. “=COUNTIF(C5:Y5,6)” I will have to explore whether countif can be also used with inequalities.

One of the most interesting things that I had not thought about was putting a picture on the background of a graph. Then by using sliders to move points you could find the slope of a line in the picture. Or you could confirm that a shape could be fit with a quadratic. Kimball uses the Luxor hotel for the slope and the Hoover dam for the quadratic.

Kimball’s session’s Excel file is worth a look. Excel experts might- like me- have one of those “Oh duh” moments. Mine was realizing that you could make a real-world example just by dropping a picture behind your graph. Kimball steps through some examples and has a couple exercises with solutions so novices can probably gain something, too.

You can use countif with an inequality. The first hit in my Google search shows how: http://www.techonthenet.com/excel/formulas/countif.php