what to do with s.f. and rounding in a series of calculations

[robert zellmer]

I may have mentioned this in lecture and you should have learned this
in 1210 (or its equivalent) but just in case here's how you should handle
sig. fig. in calculations.

When doing a series of calculations you should keep track of the s.f. in
each step but carry extra digits to the next step.  How many extra?
At least one.  I usually use store the number with lots of extra digits (in
my calculator's memory registers - which you all know how to use
after having your romantic evening with your calculator).  In lecture I
often carry several extra digits and underline the last significant digit.

On a quiz, you should carry extra digits and round the final answer.  Doing
this prevents what we call "round-off" error.

For lab, in the sample calculations you determine a number for a step, 
including
extra digits.  Then write it with the correct number of s.f. (and units 
of course).
If the number is required in the report (presentation of data section, 
table, etc. )
you record it there with the correct s.f.  If you need to use the number 
in a
subsequent calculation you should use the un-rounded number (with the extra
digits).

Hopefully this makes sense.

Dr. Zellmer