# Am I the only one that does this?

1. Oct 10, 2011

### 1MileCrash

When I get an answer in my calculator, I write down all of the decimal places until I get to one that is below 5 because I'm too lazy/indecisive to actually pick a place to round and do it.

I'm talking 6 or 7 places sometimes.

I can't be the only one?

2. Oct 10, 2011

### bp_psy

Yes, You are some kind of weirdo.:tongue2:
Anything more than two decimals is usually lying.

3. Oct 10, 2011

### DaveC426913

Concurrence. Weirdo.

4. Oct 10, 2011

### QuarkCharmer

Not only do I do that, if the 5 comes too soon (within 5-8 digits), I will continue on to the next 5. No idea why I do this. Intermediate values, oh wow, I save 20 places sometimes...

5. Oct 10, 2011

### DaveC426913

It is merely a quirk, Quark.

6. Oct 10, 2011

### arildno

I always seek the double 3's.

7. Oct 10, 2011

### Maroc

Anything more than 2 decimals is a no go in my books :P

8. Oct 10, 2011

Staff Emeritus
I take off points for insignificant digits.

9. Oct 10, 2011

### ArcanaNoir

There are no insignificant digits in my math. Usually it's pure until the answer pops out in terms of pi. Then I can take the decimal place as far as I like. This isn't physics.

Usually I look for a 0, 1, or 9. Those are my happy number rounding places.

10. Oct 10, 2011

### GregJ

As a rule of the thumb, I usually use as many significant digits as the question has.

11. Oct 10, 2011

### Staff: Mentor

If it's the final answer to a question, it should be rounded to whatever number of sig figs is appropriate for the initial input numbers.

If it's an intermediate answer, it should stay in your calculator (that's what your calculator's memory is for) and not be written down at all, unless your question asks you to show that answer also. In that case you should round off the written version appropriately, but use the unrounded version in the calculator for further calculations.

12. Oct 10, 2011

I round $e$ to 3. Is that bad?

13. Oct 10, 2011

Staff Emeritus
Not as bad as rounding it to 4.

14. Oct 10, 2011

### QuarkCharmer

No joke, my physics professor usually uses 10 for g when working examples.

15. Oct 10, 2011

### FlexGunship

Gentlemen!! We have a winnar!

16. Oct 10, 2011

### Staff: Mentor

As an engineer, I have too many assumed values in my calcs for sig figs to matter.

17. Oct 10, 2011

### Pythagorean

And this is basically how I stopped the habit in my undergrad

18. Oct 10, 2011

### ArcanaNoir

See, my problems are exact. It's not until the final calculation that things get decimal-ized.

19. Oct 10, 2011

### 1MileCrash

I don't do it for final answers, because then its just wrong, its assuming a known value for values that aren't known (or equivalently, assuming that all decimal places after the given measurement are zeros)

You will find it surprising how many students at the college level don't know the reasoning behind significant figures and think that more decimal places means a more accurate answer.

1.3 meters is not 1.30 meters, it means we stopped measuring after a tenth of a meter.

I never learned that concept in school when I learned about significant figures. It only came to me when actually doing lab work.

20. Oct 10, 2011

### ArcanaNoir

I did learn that. My most confusing times currently are when I get to the end of a probability question and the final move turns out an enormous fraction which practically requires a decimal conversion to be useful comparatively. How far do I take it? As far as I like is my guess. So, that's to a 0, 1, or 9.