Rules for Significant Figures

 

To determine the number of significant figures in a number use the following 3 rules:

 

  1. Non-zero digits are always significant
  2. Any zeros between two significant digits are significant
  3. A final zero or trailing zeros in the decimal portion ONLY are significant

Example:  .500 or .632000 the zeros are significant

                 .006  or .000968 the zeros are NOT significant

 

 

For addition and subtraction use the following rules:

 

  1. Count the number of significant figures in the decimal portion ONLY of each number in the problem
  2. Add or subtract in the normal fashion
  3. Your final answer may have no more significant figures to the right of the decimal than the LEAST number of significant figures in any number in the problem.

 

 

For multiplication and division use the following rule:

 

  1. The LEAST number of significant figures in any number of the problem determines the number of significant figures in the answer. (You are now looking at the entire number, not just the decimal portion)

*This means you have to be able to recognize significant figures in order to use this rule*

      Example: 5.26 has 3 significant figures

                      6.1 has 2 significant figures

 

 

 

Please also see Appendix A pg 587 of your textbook