October 26 2010 -- Significant Digits

Today we reviewed the significant digits (or significant figures).

A significant digit is any digit that contributes to giving precision for a number.

Non-zero digits are always significant, however, zeroes follow rules based on their position within a number :

1. Zeroes placed before other digits are not significant; 0.046 has two significant digits.
2. Zeroes placed between other digits are always significant; 4009 kg has four significant digits.
3. Zeroes placed after other digits but behind a decimal point are significant; 7.90 has three significant digits.
4. Zeroes at the end of a number are significant only if they are behind a decimal point as in (c). Otherwise, it is impossible to tell if they are significant.

We also learned how to write answers in proper form; in multiplication/division calculations, the answer must have the same number of significant digits as the number with the lowest amount of significant figures within the problem. In addition/subtraction calculations, the answer must have the same number of decimal places as the number with the lowest amount of decimal places within the problem.