*Rules
***for counting significant Figures (MISC**)

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. *Zeros. *There are three classes of
zeros:

a. *Leading zeros *are zeros that *precede
*all of the nonzero digits. They *never *count as significant figures.
For example, in the number 0.0025, the three zeros simply indicate the position
of the decimal point. The number has only two significant figures, the 2 and
the 5.

b. *Captive zeros *are zeros that fall *between
*nonzero digits. They *always *count as significant figures. For
example, the number 1.008 has four significant figures.

c. *Trailing zeros *are zeros at the *right
end *of the number. They are significant only if the number is written with a
decimal point. The number one hundred written as 100 has only one significant
figure, but written as 100., it has three significant
figures.

3. *Exact numbers. *Often calculations
involve numbers that were not obtained using measuring devices but were determined
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. Exact numbers can also arise from definitions. For example, 1 inch is
defined as *exactly *2.54 centimeters. Thus in the statement 1 in. = 2.54
cm, neither 2.54 nor 1 limits the number of significant figures when it is
used in a calculation.

You will find this chart at the bottom of
page 25 and top of page 26 in your textbook.