The accuracy of a numerical value may be indicated by the number of digits in the value given. We say that 15.6 has three significant digits, when the last decimal digit 6 may not be completely certain. The addition of more digits (for example, 15.620478) would be meaningless.
In multiplications and divisions, the number of significant digits in the final result should be the same as the number of significant digits in the least accurate factor.
EXAMPLE(36.479×2.6)/14.85 = 6.3868956 = approximately 6.4. Although extra digits are kept in the intermediate steps of the calculation, the final result has only two significant digits, because the original factor 2.6 has only two significant digits. |
In additions and subtractions, the number of digits after the decimal point in the final result should be the same as the smallest number of digits after the decimal point in the terms of the sums or differences.
EXAMPLE17.524 + 2.4 - 3.56 = 16.364 = approximately 16.4. The final result has only one digit after the decimal point because the original term 2.4 has only one digit after the decimal point. |
Taken from R. H. B. Exell, www.jgsee.kmutt.ac.th/exell/PracMath/ErrorAn.htm