As a high school teacher (both physics and chemistry) I focus on significant
figures where the data is given in a problem. In a textbook problem how is a
student supposed to determine the "precision" of an answer without some basic
rules. I tell students that it should be "easy" in the lab - they are doing
the measurements so they should know the uncertainty of their own measurements
but from others measurements don't we need some kind of "rule" to follow?