7.1 Rules to determine the significant figures

  Basic Mathematics and Measurements

Rule 1: All non-zero digits are significant. e.g. $123$ has three significant figures.

Rule 2: All the zeros between two non-zero digits are significant, no matter where the decimal point is, if at all. e.g. $108.09$ and $10207$ have five significant figures each.

Rule 3: If the number is less than $1$, the zero(s) on the right of decimal point, but to the left of the first non-zero digit are not significant. e.g. $0.0072$ has two significant figures,

Rule 4: The terminal or trailing zero(s) in a number without a decimal point are not significant. e.g. $13200$ has three significant figures.

Rule 5: The trailing zero(s) in a number with a decimal point are significant. e.g. $6.500$ has four significant figures.

Note:

• The power (or exponent) of $10$ is irrelevant to the determination of significant figures, e,g, $4.100 \times 10^3$ has four significant figures.
  
  
• The change of units only change the order of exponent but not the number of significant figures. e.g. $2600\ m=2.600 \times 10^2\ cm=2,600 \times 10^3\ mm=2.600 \times 10^{-3}\ km$. Every notation has four significant figures.
  
  
• The digit $0$ conventionally put on the left of a decimal for a number less than $1$ is never significant. e.g. $0.125$ has three significant figures.