sig figs in addition problems

[Sonia_Lele_2K]

Is there any specific reason why only the sig figs after the decimal are counted in addition or subtraction problems?

[Manali Ghadiali 1E]

The rule for determining significant figures with addition and subtraction problems is to round to the place of the least accurate number. This doesn't necessarily limit the rounding of significant figures to decimal places, but simply to the least accurate place.

Example:
223.2 + 14.234 + 6 = 243.434
If this number was to be written with the proper amount of significant figures, the answer would be 243. This is because 6 is only written to the ones place, which means that it is the least accurate digit and therefore the answer should be rounded to that same place.