[big]

How many significant figures should be reported in the answer to the calculation (Assume all numbes are experimentally determined):

(12.501*3.52/0.0042)+6.044?

So using 2 sig figs for just the multiplying and dividing, I got that it will become: 1.0*10⁵+6.044 = 10006. However, am I supposed to use 5 sig figs or 2 sig figs then for this type of addition?

[rabolisk]

It should be 2.

[Borek]

I got that it will become: 1.0*10⁵+6.044 = 10006

That's incorrect, you should not round down before adding. Calculate using full accuracy available, round down at the end. It happens in this case it won't change the final result, but that's the common source of errors.

[big]

It should be 2.

Can you explain that please? I'm not seeing why it's 2 if there's an addition sign in there.

[opti384]

I also think that the final number of sig figs will not be 2.

[rabolisk]

It is 2. Let's say that you know that the population of a city is 150000. However, only the first 2 digits are accurate. You know for a fact that it is between 145000 and 155000, but you can only report it to 150000 with certainty. Now imagine that 100 extra people move into your city. Will you now say that your population is 150100, or still 150000?

[opti384]

Yes 2 sig figs will be for this part 12.501*3.52/0.0042.

However, after you add you don't get the least sig fig number for your result like in dividing or multiplying.

[rabolisk]

The rule for addition is different from the rule for multiplication

http://www.chem.tamu.edu/class/fyp/mathrev/mr-sigfg.html

The first doubtful digit in 1.0 * 10⁵ is the 0. 6.044 makes no difference because all of those digits are to the right of the 0 of 1.0 * 10⁵. Again it only makes sense that if you have 150000, but you can only say for certain that it is somewhere between 145000 and 155000, then adding 6 does not change what you report.