SIGNIFICANT FIGURES

The significant figures of a number are those digits that carry meaning contributing to its precision.

Specifically, the rules for identifying significant figures when writing or interpreting numbers are as follows:

• All non-zero digits are considered significant. For example, 91 has two significant figures (9 and 1), while 123.45 has five significant figures (1, 2, 3, 4 and 5).
• Zeros appearing anywhere between two non-zero digits are significant. Example: 101.1203 has seven significant figures: 1, 0, 1, 1, 2, 0 and 3.
• Leading zeros are not significant. For example, 0.00052 has two significant figures: 5 and 2.
• Trailing zeros in a number containing a decimal point are significant. For example, 12.2300 has six significant figures: 1, 2, 2, 3, 0 and 0. The number 0.000122300 still has only six significant figures (the zeros before the 1 are not significant). In addition, 120.00 has five significant figures since it has three trailing zeros. This convention clarifies the precision of such numbers; for example, if a measurement precise to four decimal places (0.0001) is given as 12.23 then it might be understood that only two decimal places of precision are available. Stating the result as 12.2300 makes clear that it is precise to four decimal places (in this case, six significant figures).
• The significance of trailing zeros in a number not containing a decimal point can be ambiguous. For example, it may not always be clear if a number like 1300 is precise to the nearest unit (and just happens coincidentally to be an exact multiple of a hundred) or if it is only shown to the nearest hundred due to rounding or uncertainty. 

Determine the number of significant figures in each of the following:
 

a) 3427	b) 0.00456	c) 123,453
d) 172	e) 0.000984	f) 0.502
g) 3.01 x 102	h) 1.14 x 104	i) 107.2
j) 0.0000455
		Answers: 4, 3, 6, 3, 3, 3, 3, 3, 4, 3