Significant Figures in Derived Results: GO BACK
Addition & Subtraction
- Find the last significant digit in each number to be
added or subtracted (the colored numbers below).
- Determine which number has the greatest
uncertainty. It will be the one with the last significant digit
farthest to the left in the column of numbers.
- In the number with the greatest uncertainty, the place
of the last significant digit represents the place of the last significant
digit in the final answer.
The answer must be rounded so that it contains the same
number of digits to the right of the decimal point as there are in the
measurement with the smallest number of digits to the right of the decimal
In the examples below, the significant figures are colored
blue and the uncertain digits are bold.
207.2 = 210
The tens place. 1, is the last place a digit it kept in
the final answer. The zero is a place
The ones place, 4, is the last place a digit
is kept in the final answer.
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