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Rules for Significant Figures

 

Version Number 1

Rule #1: All non-zero digits are significant.

Rule #2: Zeros in front of a number are not significant.

Rule #3: Zeros between non-zero digits are significant.

Rule #4: Zeros at the end of a number are significant if there is a decimal point in the number.
 

Version Number 2

Use this diagram to help determine the number of significant figures in a measured value…

            Pacific                          Atlantic          

If the decimal point is present, start counting digits from the Pacific (left) side,

          starting with the first non-zero digit.  

    0.003100     

(4 sig. figs.)

 

If the decimal point is absent, start counting digits from the Atlantic (right) side,

starting with the first non-zero digit.  

    31,400     

( 3 sig. figs.)

Examples

HIGHLIGHT TO REVEAL ANSWER

0.0203    3 significant figures
2.50    3 significant figures
2500    2 significant figures
3.7 x 109    2 significant figures
45009    5 significant figures
100.    3 significant figures
10200 3 – the zeros 10200 are ambiguous and 10200 is trapped
34000.00 7 – the zeros 34000.00 indicate precision and 34000.00 are trapped
0.0600 3 – the zeros 0.0600 are place holding and 0.0600 indicate precision
0.0058363 5 – the zeros 0.0058363 are place holding
  0.508   3 – the zero 0.508 is place holding and 0.508 is trapped
5007.00     6 – the zeros 5007.00 are trapped and 5007.00 indicate precision
2.40 x 104  3 – the zero indicates precision
0.005670  4 – the 0.00 part is for place holder and the trailing zero is significant
54000 2 – the zeros in 54000 are ambiguous since the decimal is not shown
0.025 2 – the zeros 0.025 are placeholders zeros only

Chemical Demonstration Videos

 
Significant Figures