General Rules for Determining Number of Significant Figures
All nonzero digits are significant.
Zeros are also significant with two exceptions:
Terminal zeros preceding the decimal point in amounts greater than one is an ambiguous case.
Rules for Numbers WITHOUT a Decimal Point
START counting for sig. figs. On the FIRST non-zero digit.
STOP counting for sig. figs. On the LAST non-zero digit.
Non-zero digits are ALWAYS significant.
Zeroes in between two non-zero digits are significant. All other zeroes are insignificant.
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