Signficant Number question!

[voidflux]

Hello everyone, this question has been bothering me, I was refreshing my signinficant number rules when one of the examples said the result should be .082 or 8.2E-2; here's the problem:

(2.560)(8.8)
--------------- =    
    275.15

22.528
---------  = 
275.15

0.0818753 = 0.082 = 8.2E-2;

okay now this all makes sense until the last part when they changed 0.0818753 to 0.082. Becuase by the rules of mutliplication and division of sigfigs it says, the result should be the same as the number in the least precise measurement used in the calcuation. now does this mean, the current calculation:
22.528/275.15 or does it mean in the whole calculation? If the first case is true then the result should have 5 sig figs, if the 2nd case is true then the calculation should have 2 sig figs, since 8.8 only has 2 sig figs

[nishantp]

As stupid as this sounds, this seems to vary among my teachers


I generally stick with the 2nd case, that you should take the number of sig digs from the least precise value in the entire problem, not just that calculation.

[voidflux]

Thanks for the info!! Thank god I only have Chemistry my first semiester! but i'm sure Physics will use sig figs

[DiGiTaIErRoR]

Originally posted by voidflux
Thanks for the info!! Thank god I only have Chemistry my first semiester! but i'm sure Physics will use sig figs

There was greater use of the significant digits in my Chemistry class than Physics.

[voidflux]

In highschool my physics teacher didn't use sig figs at all! I wish he did though so I didn't have to reteach myself the rules before I go to college! I always hate when I miss -3 points on a test becuase I forgot about sig figs, its disturbing! but thats life

[sql_lall]

Ok, as a general rule-of-thumb, that i have been taught throughout schooling is:
1) Collect the values
(in this case the 2.56, 8.8 and 275.15)
Now, beacuse these are your RAW data, these are what your answers are based on, so the accuracy of your data is only as good as the least accurate Raw data, so 2 sig. figs it is
2) Work everything out, ignoring rounding/sig. figs. Then, when you get the final answer, round it off.

Basically, you have to use only the accuracy of the least accurate raw data. In the example, you can't say that 22.528 is accurate to 5 s.f, as one of the things used to work it out (8.8) is only accurate to 2 s.f