SIGNIFICANT DIGITS
Review of Introductory Mathematics
Both the precision of numbers and the number of significant digits they contain must be
considered in performing arithmetic operations using numbers which represent measurement. To
determine 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 except
when there is a decimal point in the number, in which case the right-most
digit, even if it is zero, is called the least significant digit.
Rule 3:
The number of significant digits is then determined by counting the digits
from 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 significant
digit in the sum is in the same position as the left-most least significant digit in the numbers
added or subtracted.
Example:
15.62 psig + 12.3 psig = 27.9 psig
Example:
401.1 + 50 = 450
Example:
401.1 + 50.0 = 451.1
MA-01
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