Hello fellow math teachers! I am hoping that one of you has an idea for teaching students when/why some digits are significant and why trailing zeros are inconsequential. I have tried equating it to money, but the concept is just so abstract that they are not getting it. I can tell them a bunch of rules, but that won't stick. Any ideas? Thanks!

I never learned sig figs in math. I learned them for the first time in chemistry. Maybe applying it to chemistry will help. http://www.dartmouth.edu/~genchem/sigfigs.html

Yeah, I learned sig figs in my science classes, but math never went near them. Math teachers tend to prefer fractions anyway. Sig figs really just are a convention that was agreed to by people. There isn't a deep how/why like with some of the other topics.

Do they already know Order of Operations? I think you can almost explain it like that...it's an agreed-upon convention so that we all have the same results. If people just rounds however they wanted, it would be confusing to understand the rules he/she used.

Is this if any help?? http://www.teachforever.com/2009/01/lesson-idea-significant-figures-made.html or this? http://www.youtube.com/watch?v=5UjwJ9PIUvE (sorry, I only gave these a quick glance; you'll have to really preview them before using.)

I don't know why sig.figs.would be taught to all students. I think the following discussion would be sufficient to get interested students started. How many Sig.figs.in the following? 3000 which could mean 2500 to 3499, 3500 which could mean 3450 to 3549, 3550 which could mean 3545 to 3554, 0.0003 which could mean 0.00025 to 0.00034. Then ask why put a zero after a decimal. We can not write 0.0003 as 0. 3. Also 0.30 might be exactly 30 one-hundredths rather than 29 one-hundredths or 31 one-hundredths. Why learn sig.figs.? The reason is to learn the efficiency of Scientific Notation as follows for example: 3.000 x 10^3 means exactly 3000, 3.500 x 10^3 means exactly 3500, 3.550 x 10^3 means exactly 3550, 3 x 10^-3 means exactly 0.0003, 3.0 x 10^-1 means exactly 0.30. I think – don’t even feel it is important enough to check myself. Now what can we do with such skill? Discuss the following prob. Before NCLB, 300 students in a district needed to learn sig.figs., and 2 math teachers were needed. After NCLB, 3000 students in the district needed to learn sig.figs., and 100 math teachers were needed. How much money was needed for all this?

I am sort of sad to admit that my head just exploded. I think I need to take a lesson in significant digits! Thanks for the help!!! Does anyone think this is sort of an odd thing to teach in a 7th grade math class...or am I just not getting this?

Thank you so much for the links. They were both pretty helpful. I will actually admit that I did not understand all of the rules fully until I checked this out. It's pretty sad I think...The first link was really great, but the person who posted it didn't realize that the last 2 slides (the most important by the way!) loaded with a big picture in front of her text! Oh well. Thanks again for the help.

Is this one any better? http://www.teachertube.com/viewVideo.php?video_id=123662&title=Significant_Figures Again, sorry to be so lazy; the sound is out on my computer, so I haven't previewed.