digits than the significant digits is superfluous and also misleading since it would give a wrong idea about the precision of measurement. The rules for determining the number of significant figures can be understood from the following examples. Significant figures indicate, as already mentioned, the precision of measurement which depends on the least count of the measuring instrument. A choice of change of different units does not change the number of significant digits or figures in a measurement.
This important remark makes most of the following observations clear: ( ) For example, the length . cm has four significant figures. But in different units, the same value can be written as .02308 m or . mm or 23080 µ m.
All these numbers have the same number of significant figures (digits , , , ), namely four. This shows that the location of decimal point is of no consequence in determining the number of significant figures. The example gives the following rules : All the non-zero digits are significant. All the zeros between two non-zero digits are significant, no matter where the decimal point is, if at all.
If the number is less than , the zero(s) on the right of decimal point but to the left of the first non-zero digit are not significant. [In . , the underlined zeroes are not significant]. The terminal or trailing zero(s) in a number without a decimal point are not significant.
[Thus m = 12300 cm = 123000 mm has three significant figures, the trailing zero(s) being not significant.] However, you can also see the next observation. The trailing zero(s) in a number with a decimal point are significant. [The numbers . or .06900 have four significant figures each.] ( ) There can be some confusion regarding the trailing zero(s).
Suppose a length is reported to be . m. It is evident that the zeroes here are meant to convey the precision of measurement and are, therefore, significant. [If these were not, it would be superfluous to write them explicitly, the reported measurement would have been simply .
m]. Now suppose we