What do you mean by significant figures? State the rules for deciding significant figures.

i. The significant figures in a measurement or result are the number of digits known with certainty plus one uncertain digit.

ii. Rules for deciding significant figures : 

a. All non-zero digits are significant. 

e.g. 127.34 g contains five significant figures which are 1, 2, 7, 3 and 4.

b. All zeros between two non-zero digits are significant, e.g. 120.007 m contains six significant figures.

c. Zeros on the left of the first non-zero digit are not significant. Such a zero indicates the position of the decimal point. e.g. 0.025 has two significant figures, 0.005 has one significant figure.

d. Zeros at the end of a number are significant if they are on the right side of the decimal point,e.g. 0.400 g has three significant figures and 400 g has one significant figure.

e. In numbers written is scientific notation, all digits are significant. e.g. 2.035 × 10² has four significant figures and 3.25 × 10^-5 has three significant figures.