As a result of mentoring this week's Math Forum MidPoW, Altius, Citius, Fortius, I have been thinking a lot about significant digits. Let's see if I can give you a quick summary of the problem so you'll be able to see what I'm talking about.
Various Olympic and World record times for both speed skaters and runners are given for the 1500 meter races. The first question asks students to determine whether any of these athletes would be arrested if they were skating or running at their record speed in a 25 mile per hour residential zone. The idea of significant digits is appropriate to discuss as far as how students express their answers but it really became an issue when I started reviewing the bonus question responses!
The bonus question is: "Let's imagine the speed skater and runner from each year starting a race side by side. How far behind is each runner when the skater crosses the finish line?"
All of the students who did the bonus, were getting answers just a tad different than the ones I had and yet there was no real consistent difference. Annie Fetter came to the rescue and worked out the solution using both my method and the students' method and realized that the reason that my numbers did not agree was because I had rounded off too much and too early. It made me realize what an important, yet perhaps often ignored, subject significant digits are.
So, given this background information, here is what I'm now very interested in hearing about from you:
1. At what age do you teach your students about significant digits? What age do you think this is normally taught?
2. Do you have a favorite activity that you use to teach your students about significant digits?
By the way, you're welcome to view the problem itself by going to http://mathforum.org/midpow - if you'd like to see the clues and all, just submit but tell me that you are a "math-learn" member just viewing. Once you've gotten in to the problem area, all of the features will be available for viewing.
------- Suzanne Alejandre Educational Resource and Service Developer The Math Forum @ Drexel [http://mathforum.org]