Rules for determining significant figures
1. All nonzero digits are significant.
2. All zeroes between nonzero digits are significant.
3. Zeroes to the right of a nonzero digit, but to the left of an understood
decimal point, are not significant.
If such zeroes are known to have been measured, however, they are
significant and should be specified as such by inserting a decimal point to the
right of the last zero.
4. In numbers less than one, zeroes to the right of a decimal point that are
to the left of the first nonzero digit are never significant.
They are simply placeholders.
5. In numbers less than one, the zero to the left of the decimal point is
6. All zeroes to the right of a decimal point and to the right of a nonzero
digit are significant.
Addition and Subtraction Involving Significant Figures
In addition or subtraction, the arithmetic result should be rounded off so that the final digit is in the same place as the leftmost uncertain digit.
Multiplication & Division Involving Significant Figures
The arithmetic product or quotient should be rounded off to the same number of significant figures as in the measurement with the fewest significant figures.