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 Zeros used solely for spacing the decimal point (place holders) are not significant. So
zeros appearing in front of nonzero digits are not significant, because they are only
placeholders, for example:0.093827 has five significant figures 0.0008 has one significant
figure 0.012 has two significant figures.
 The trailing zeros in a number without a decimal point are insignificant. For example
2304000 has four significant figures.
 Trailing zeros that aren't needed to hold the decimal point, i.e., the additional zeros to the
right of both the decimal place and another significant digit are significant. For example,
4.00 has three significant figures.
 The significant digit in a number that is furthest to right is called least significant digit. For
example, the least significant digit in 3.456 is 6
b
 For a measurement reported in scientific notation i.e in the form a x 10 , all the digits in the
base number ‘a ‘ are significant. The power of 10 is irrelevant in the determination of
significant figures.
3
-3
2
3.560 m= 3.560 x 10 km = 3.560 x 10 cm =3.560 x 10 mm. Each number in this case has
four significant figures.
Significant figures in algebraic operation
Rule-1
When numbers are multiplied or divided, the result has the same number of significant figures as
are in the original number with the least significant figures.
Rule-2
When numbers are added or subtracted, there should be as many decimal places retained in the
final result as are there in the number with the least decimal places.

Rounding off the uncertain digits
 If the insignificant digit to be dropped is more than 5, the preceding digit is raised by 1.
 If the insignificant digit to be dropped is less than 5, the preceding digit is left unchanged.
 If the insignificant digit to be dropped is 5, the preceding digit is raised by 1 if it is odd ,
and is left unchanged if it is even.

Dimensions
Dimensions of a physical quantity are the powers to which the base quantities are raised to
represent that quantity.
 The dimension of length is [L].
 The dimension of mass is [M] .
 The dimension of time is [T] .
 The dimension of electric current is [ A] .

 The dimension of thermodynamic temperature is [ K] .
 The dimension of amount of substance is [mol] .
 The dimension of luminous intensity is [cd] .