Sig figs

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From: Geoff Ruth (gruth@uclink4.berkeley.edu)
Date: Wed Aug 30 2000 - 14:39:49 PDT 

Message-Id: <v04011701b5d32e1cb25e@[128.32.190.180]>
Date: Wed, 30 Aug 2000 13:39:49 -0800
From: Geoff Ruth <gruth@uclink4.berkeley.edu>
Subject: Sig figs

Hi y'all,

Today I introduced sig figs to my students, and immediately ran into some
problems. One of the standard rules for dealing with sig figs is that any
zeros after the decimal place and before the first non-zero digit are
insignificant (ie 0.003 has one sig fig). My students had a hard time
grasping why you'd drop these leading zeros.

One way that I tried to explain this to them was by thinking about a more
concrete example: If you start with 3 g of something, and then convert that
into milligrams, you'd have 0.003 mg. Obviously, the measurement doesn't
become more precise as you do the unit conversion, so the milligram
measurement should have the same # of sig figs as the first.

I was pretty psyched about this explanation, but some students needed to
approach the question from another perspective. I *really* don't want them
to learn a bunch of rules without understanding them. Can anyone help me
out with an alternative, conceptual way to explain sig figs?

Thanks!

Geoff Ruth
Leadership High School
300 Seneca Avenue
San Francisco, CA 94112

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