[Big-Daddy]

How many times can we repeat the same?

Rule says:

When adding or subtracting using significant figures rules, results are rounded to the position of the least significant digit in the most uncertain of the numbers being summed (or subtracted). That is, the result is rounded to the last digit that is significant in each of the numbers being summed. Here the position of the significant figures is important, but the quantity of significant figures is irrelevant.

Sum is:

  1.77
  2.4
  0.973
255.
-------
260.143

The last digit of the most uncertain number is the second 5 in 255, so we round to whole numbers - hence 260, with three significant digits. In scientific notation it is 2.60x10².

What is the definition here of "most uncertain number"?

[Arkcon]

Can you figure it out from the reference provided above: http://en.wikipedia.org/wiki/Significance_arithmetic#Addition_and_subtraction_using_significance_arithmetic

[Borek]

Different wording of the same rule:

When quantities are being added or subtracted, the number of decimal places (not significant digits) in the answer should be the same as the least number of decimal places in any of the numbers being added or subtracted.

Note that decimal place can refer to digit to the left of the decimal point (units, tens, hundreds and so on).