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What are Sig Figs?
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Significant Figures Definition

Significant figures (sig figs) are the digits in a number that carry meaningful information about its precision. This includes all digits except:

  • Leading zeros (0.0045 has 2 sig figs)
  • Trailing zeros when no decimal is present (4500 has 2 sig figs)
Why are significant figures important?

Significant figures indicate the precision of a measurement. Using the correct number ensures calculations don't imply more precision than actually exists.

Counting Significant Figures

  1. All non-zero digits are significant (1-9)
  2. Zeros between non-zero digits are significant (1003 has 4 sig figs)
  3. Leading zeros are never significant (0.0045 has 2 sig figs)
  4. Trailing zeros are significant only if the number contains a decimal point (45.00 has 4 sig figs)

Rounding Rules

  1. If the digit after the last significant figure is less than 5, round down
  2. If 5 or greater, round up
  3. For exactly 5, round to make the last digit even ("banker's rounding")

How many significant digits are there in...

Example 1: 0.004560

This number has 4 significant figures (4560). The leading zeros are not significant.

Example 2: 1234.00

This number has 6 significant figures. The trailing zeros after the decimal are significant.

Example 3: 1200

This number has 2 significant figures (typically). Without a decimal point, trailing zeros are ambiguous.

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