SIGNIFICANT FIGURES AND RULES FOR COUNTING SIGNIFICANT FIGURES
SIGNIFICANT
FIGURES
“All the accurately known digits in a
value and the first doubtful digit are known as significant figures.” In the measurement of any physical
quantity the number of digits about which we are sure are called significant
figures All physical measurements involve some degree of inaccuracy due to
human error. instrumental error or due to both and therefore the knowledge of
precision of a measurement is very important. A significant figure is that
which is known to be reasonably reliable. The last figure being reasonably
correct guarantees the certainty of the preceding figures.
RULES FOR COUNTING SIGNIFICANT
FIGURES:
(i) In whole
number values. all the digits except zeros at the right side m recognized as
significant figures.
(ii) In
decimal number values the zeros at the right side of the number are counted as significant
figures but the zeros at the left side are not taken as significant figures.
(iii) Power
or exponents to a certain base are not taken as significant figures.
(iv) In
addition and subtraction process, the result should be rounded off to contain
as many as decimal places as contained in the value of least number of decimal
place.
(v) In
multiplication and division process. the result should be rounded off to
contain as many as significant figures as contained in the factor of least
significant figures.
FOR EXAMPLE:
S.NO

Value

No.
of significant figures

1

0.00045

2(4,5)

2

1.2000

5(1,2,0,0,0)

3

505

3(5,0,5)

4

34000

2(3,4)

5

6.67 x 10^{32}

3(6,6,7)

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