2.  1. Nonzero integers. Nonzero integers always count as significant figures. For example, the number 1457 has four nonzero integers, all of which count as significant figures.  2. Exact Numbers. Often calculations involve numbers that were not obtained using measuring devices but were determine by counting: 10 experiments, 3 apples, 8 molecules. Such numbers are called exact numbers. They can be assumed to have an unlimited number of significant figures.

3. 3. Zeros. There are three classes of zeros: a. Zeros between nonzero digits are always significant – 1005 (4 sig figs), 1.03 (3 sig figs) b. Zeros at the beginning of a number are never significant; they merely indicate the position of the decimal point – 0.02 (1 sig fig), 0.0026 (2 sig figs) c. Zeros at the end of a number are significant if the number contains a decimal point – 0.0200 (3 sig figs), 3.0 (2 sig figs), 5000 (1 sig fig)

4.  The results contains the same number of significant figures as the measurement with the fewest significant figures.  6.221cm x 5.2cm = 32.3492 cm 2 = 32cm 2 We round off the to two significant figures because the least precise number, 5.2cm, has only two significant figures.

5.  For addition and subtraction, the result has the same number of decimal places as the measurement with the fewest decimal places. Consider the following example  20.42 - two decimal places  1.322 - three decimal places  +83.1 - one decimal place (limits the # of sig figs)  104.842  We report the result as 104.8 because 83.1 has only one decimal place.