The result of a measurement should be consistent with the measuring instrument used. If the instrument only measures up to hundredths and due to intermediate calculations we have a result which goes to thousandths, we have to round this up to hundredths, increasing them or leaving the number of hundredths that we started with.
To understand how to round, you must already understand the degree of precision in the result of a measurement. You should also remember that:

  • The number of significant figures in the result is determined by the degree of precision.
  • The least significant figure of the result is of the decimal order determined by the significant figure of the degree of precision.
    Example: 34.123 ± 0.001. The significant figure of the degree of precision corresponds to the thousandths and the least significant figure of the result (the 3) is in the order of the thousandths.

The following table presents a series of examples with incorrect rounded expression and their corresponding correct expression.

Incorrect

Correct

453 ± 0,51

453. 0 ± 0. 5

0. 0237 ± 0.01

0. 02 ± 0. 01

5. 897 ± 0.028

5.99 ± 0.03

56.789 ± 0.138 56.79 ± 0.15
34567 ± 3427 34000 ± 3000

332 ± 120

300 ± 100