In most math classrooms numbers are not measured, and often rounding decimals is arbitrary. In science, however, the number of decimal places tells you how accurately a value is measured. The number of digits are called significant figures. Not all tools are created equal. The three pieces of glassware below have the same amount of water in them; however, the buret has the most markings (graduations), and therefore is able to get a more accurate measurement.
**Notice that the buret only has graduations that show tenths of a ml. But the value reported is measured to the hundredths decimal place. The last digit of each number is always estimated. **
All non-zero digits are significant
ex. 12345 has 5 sig figs
2. Zeroes between non-zero digits are significant (sandwich rule)
ex. 101 has 3 sig figs
3. Zeroes to the left of non-zero digits are NOT significant
ex. 0.001547 has 4 sig figs
4. With a decimal in the number zeores to the right of non-zero digits are significant
ex. 125.00 has 5 sig figs
5. count all the digits in the first half of a number in scientific notation
ex. 3.050 x 102 has 4 sig figs
6. Exact values have an infinite number of sig figs.
ex. There are exactly 60 seconds in 1 minute