SIGNIFICANT DIGITS Review of Introductory MathematicsBoth the precision of numbers and the number of significant digits they contain must beconsidered in performing arithmetic operations using numbers which represent measurement. Todetermine the number of significant digits, the following rules must be applied:Rule 1: The left-most non-zero digit is called the most significant digit.Rule 2: The right-most non-zero digit is called the least significant digit exceptwhen there is a decimal point in the number, in which case the right-mostdigit, even if it is zero, is called the least significant digit.Rule 3: The number of significant digits is then determined by counting the digitsfrom the least significant to the most significant.Example:In the number 3270, 3 is the most significant digit, and 7 is the least significant digit.Example:In the number 27.620, 2 is the most significant digit, and 0 is the least significant digit.When adding or subtracting numbers which represent measurements, the right-most significantdigit in the sum is in the same position as the left-most least significant digit in the numbersadded or subtracted.Example:15.62 psig + 12.3 psig = 27.9 psigExample:401.1 + 50 = 450Example:401.1 + 50.0 = 451.1MA-01 Page 54 Rev. 0
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