When using theoretical calculations, it is often a good idea to express calculations and data in significant digits. A calculation has the same number of significant digits as the number in the original problem with the least amount of significant digits. Here are a few rules for significant digits.

  1. All nonzero digits are significant.
  2. All zero digits which are the final digit after the decimal point are significant.
  3. All digits in between significant digits are significant.
  4. All other digits are not significant.

You may have to use scientific notation to express some significant digit calculations, such as 49+51, which equals 100, but since "100" has one significant digit, you must express it as (1.0 * 10^2) or 1.0E2. Some practice:

  • 321: 3
  • 300: 1
  • 0.000003: 1
  • 0.300000: 6
  • 3.205: 4
  • 7.0000000000000000000: 20