Significant Figure

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Malaysia SPM Modern Mathematics, Form 4, Chapter 1, Standard Form
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1 What is Significant Figure?
2 Identifying Significant Digits
3 Number of Significant Digits After an Operation
4 Recommended Webpages

[edit] What is Significant Figure?

In measurement, significant figures indicates the certainty of the measurement. As the number of significant figures increases, the certainty of the measurement increases. In other words, we are more certain about what we have measured.

[edit] Identifying Significant Digits

The rules for identifying significant digits when writing or interpreting numbers are as follows:

All non-zero digits are considered significant. Example: 1, 20, and 300 all have one significant figure. They are 1, 2, and 3 respectively. 123.45 has five significant figures: 1, 2, 3, 4 and 5.
Zeros appearing anywhere between two non-zero digits are significant. Example: 101.12 has five significant figures: 1, 0, 1, 1 and 2.
Leading zeros are not significant. For example, 0.00012 has two significant figures: 1 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. This convention clarifies the precision of such numbers; for example, if a result accurate to four decimal places is given as 12.23 then it might be understood that only two decimal places of accuracy are available. Stating the result as 12.2300 makes clear that it is accurate to four decimal places.
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 accurate 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.
A number with all zero digits (e.g. 0.000) has no significant digits, because the uncertainty is larger than the actual measurement.

(Significant figures. (2008, November 29). In Wikipedia, The Free Encyclopedia. Retrieved 06:20, November 30, 2008, from http://en.wikipedia.org/w/index.php?title=Significant_figures&oldid=254751268)