In numbers like 1,000, etc, unless otherwise stated, the zeros are
presumed to 'be decimal-holding zeros.
(b) Rounding off.
1. The actual process of rounding off consists of dropping
digits on the right side of the figure, leaving the desired number of
significant digits. If the value of the digits dropped is over five, the
surplus digits are dropped and the last significant digit is raised one
For example, 60.25132 rounded off to three places would be 60.3.
When the value of the dropped digit is exactly five, it is considered to be
under five if dropping it would leave an odd ending. The purpose of this is
to prevent a systematic error when a great many numbers are rounded off. It
will result, however, in more rounded-off numbers ending even than odd.
2. Digits marked with a bar over (N) or under (N) then are
considered as significant with a possible error of plus or minus 1.
3. When performing calculations with approximate numbers from
meter readings or any measuring instrument, there are rules for correct
handling of these figures when they are involved in calculations.
4. When adding or subtracting approximate numbers, first,
round off the numbers one place to the right of the number that has its
least significant digit farthest to the left. Second, perform the addition
or subtraction. Third, round the result off one more place for example:
least significant digit
142.6 Rule 1, round all
farthest to the left.
165.23 Rule 2, add or
165.2 Rule 3, round one more
5. then multiplying or dividing approximate numbers, count the
significant digits in the factor having the fewest number of