# How to Teach Sig Figs [closed]

A few years ago I taught a physics class for 6th graders at a school with an accelerated curriculum. These students are good at memorizing, and following procedures, so I was able to teach them the standard rules for deciding how many significant figures to include fairly easily, but I struggled to convey the underlying principles of uncertainty and scientific communication. I tried a few different approaches, but none of them really seemed to stick. Rather than teaching the rote memorization of rules, I'd like to be able to teach the underlying concepts and principles, and how the rules are applications of those principles. Does anyone have ideas for how to explain significant figure rules in light of underlying uncertainty in a way that a (very smart) 6th grader could understand?

Ideally, I would prefer a method that follows the principles of Modeling Instruction.

• Why are people voting to close this question? "How to explain" fully fits into the education tag description, which includes "Teaching strategies". May 22, 2020 at 20:16
• Is this question really opinion-based, or was this question just closed due to anti-education bias? What would a fact-based education question look like? If there is a way to rewrite the question to be fact-based, I'd appreciate actionable feedback. If not, I'm disappointed that this site is missing great potential to be useful for the physics education community. May 26, 2020 at 12:52

I teach it by measuring things with different measuring tools and then adding or subtracting the measured numbers. For example I'll use a bathroom scale to find the mass of a big box of weights and then take one weight out and mass it on a more accurate triple beam balance. Then we calculate the new reduced mass of the box by subtraction and it looks something like 11.5 kg - 1.3413 kg = 10.1587 kg but of course you have to round off based on the significant digits. I've done the same sort of thing measuring with a tape measure and a micrometer. Showing rules for multiplication and division is a bit trickier...

• +1, because I believe this is a clever way to teach the subject of significant figures. However, I have to admit that I never paid any attention to this subject, because we actually have two different quantities: (1) the estimator, and (2) the uncertainty. So in your example the estimator is given by $10.1587kg$ and the uncertainty is approx. $0.2kg$. By stating these two quantities always together it is obvious that too many decimal places in the estimator are a wast of space. May 22, 2020 at 20:47

Try measuring a time interval with an analog clock. If you have a second hand, you might find it is 3 hours, 23 minutes, and 17 seconds.

If you just have a minute hand, it is harder to tell how many seconds. You might find it is 3 hours and 23+ minutes.

With just an hour hand, you might find it is about 3 1/2 hours.

If they are smart and hard working, maybe set them this article to read. Then do the activities that the others have said.