Hello all, I understand the rules of SF\'s in its basic concept(addition/subtrac

Question

Hello all,
I understand the rules of SF's in its basic concept(addition/subtraction vs. multiplication/division); however, whencalculating an average when using both multiplication and addition,where do you base your SF's on? The figures you are adding atthe end or multiplying at the beginning.
Example:
Naturally occurring Boron is 19.9% 10B with an atomic mass of10.013u, and 80.1% 11B with an atomic mass of 11.009u. Whatis the average atomic mass of Boron?
If I understand it correctly it should look like this:
10.013u (.199) = 1.992587 11.009u (.801) = 8.818209
1.992587 + 8.818209 = average atomic mass of Boron
But to where do I take my answer to (SF's)? Do I base iton the the multiplication or the addition after themultiplication?
Thank you.
I understand the rules of SF's in its basic concept(addition/subtraction vs. multiplication/division); however, whencalculating an average when using both multiplication and addition,where do you base your SF's on? The figures you are adding atthe end or multiplying at the beginning.
Example:
Naturally occurring Boron is 19.9% 10B with an atomic mass of10.013u, and 80.1% 11B with an atomic mass of 11.009u. Whatis the average atomic mass of Boron?
If I understand it correctly it should look like this:
10.013u (.199) = 1.992587 11.009u (.801) = 8.818209
1.992587 + 8.818209 = average atomic mass of Boron
But to where do I take my answer to (SF's)? Do I base iton the the multiplication or the addition after themultiplication?
Thank you.

Explanation / Answer

sorry was unaware you were just looking for an example. wasdoing a lab report when i saw this haha okay so you do sig figs in order of normal multiplication andaddition/subtraction rules you do sig figs for multiplication values first then you dosubtraction addition. here is an example: (2.3)(4.02) + (3.4567)(2.66) ----- (2SF)(3SF) + (5SF)(3SF) = 9.2 + 9.19 ------ (2SF) + (3SF) but use lowest decimalplace now = 18.4 hope that helps, if you want to run through some other examples orhave other questions feel free to ask.

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