Question

From your General Chemistry knowledge, what are the rules for expression significant figures in addition and subtraction?

Answer 1

very simple rule in addition and subtraction

In addition and subtraction, the answer cannot have more digits to the right of the decimal point than either of the original numbers. Consider these examples:

ex1): 89.332
                      + 1. 1               one digit after the decimal point
                   _________
                        90.432                      round off to 90.4 --------------> answer

ex2): 2.097
                   − 0.12                two digits after the decimal point
                 ________
                        1.977             round off to 1.98 -------------------> answer