Significant figure
A significant figure is each digit of a number that are required to express it with the desired accuracy.
Rules:
- Non zero digits are always significant. E.g. 54 has two significant figures, and 54.3 has three significant figures.
- Zero placed before other digits are not significant. E.g. 0.0000023 has two significant figures.
- Zero placed between other digits is always significant. E.g. 302 has three significant figures, and 4005 has four significant figures.
- Zero placed after other digits but behind a decimal point are significant. E.g. 5.30 has three significant figures.
The number of significant figures in an answer to a calculation depends on the number of significant figures in the given data.
Rules for rounding up numbers:
- If the next number is 5 or more, we round up.
- If the next number is 4 or less, we do not round up.
Example: The number 718.64 is rounded to:
- 4 significant figures: 718.6
- 3 significant figures: 719
- 2 significant figures: 720