### 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 1032 3(6,6,7)