Definition:
Significant figures are the digits in a measurement that carry meaning and contribute to its precision. They include all known digits plus one estimated digit.
Rules for Significant Figures:
All non-zero digits are significant.
Any zeros between significant digits are significant.
Leading zeros (zeros to the left of the first non-zero digit) are not significant.
Trailing zeros in a decimal number are significant, but trailing zeros in a whole number without a decimal may or may not be significant, depending on the context.
Example:
123.45 has 5 significant figures.
0.00456 has 3 significant figures (the zeros are not significant).
4500 has 2 significant figures (unless a decimal is added, e.g., 4500.0 has 5 significant figures).
Explanation:
Significant figures are important in ensuring that measurements and calculations are not over-represented with more precision than the data supports.
When performing calculations (addition, multiplication, etc.), the result should be reported with the appropriate number of significant figures based on the data used.