Significant Figures.

Significant figures are the sum total number of reliable digits and one unreliable digit. Larger the number of significant figures obtained in a measurement, greater is the accuracy of the measurement. The reverse is also true.

The following rules are observed in counting the number of significant figures in a given measured quantity.

(1) All non-zero digits are significant.

Example : 42.4 has three significant figures.

25.123 has five significant figures.

(2) A zero becomes significant figure if it appears between to non-zero digits.

Example : 5.02 has three significant figures.

2.604 has four significant figures.

2.004 has four significant figures.

(3) Leading zeros or the zeros placed to the left of the number are never significant.

Example : 0.243 has three significant figures.

0.002 has one significant figures.

(4) Trailing zeros or the zeros placed to the right of the number are significant.

Example :  5.330 has four significant figures.

533.00 has five significant figures.

                        743.000 has six significant figures.

(5) In exponential notation, the numerical portion gives the number of significant figures.

Example :  1.42 * 10^–2 has three significant figures.

1.42 * 10⁴ has three significant figures.