The significant figures are normally the measurement of a number that includes all digits in the number that is known reliably plus first digit that is uncertain. The digit that are known reliably plus the first uncertain digit are known as significant figures or digits.
Example:- let a measured distance is reported as 374.5 m. It has 4 significant figure 3, 7, 4 and 5, because 3, 7 and 4 are certain digit while 5 is uncertain digit.
Rules For Determining Significant Figure
1. All non zero digits are significant.
Example:- X = 1234 has 4 significant figure.
2. All the zeros between two non zero digits are significant, no matter where, the decimal point is if at all.
Example:- X = 1007 or X = 10.07 has 4 significant figure.
3. If the number is less than 1, the zero on the right of decimal point and to the left of first non-zero digit are not significant.
Example:- X = 0.005704 has 4 significant figure 5,7,0 and 4.
4. In a number without a decimal point, The terminal or trailing zeros are not significant.
Example:- X = 3210 has 3 significant figure 3,2 and 1.
5. The trailing zero in a number with a decimal point are significance.
Example:- X = 3.500 has 4 significant figure 3,5,0 and 0.
6. The multiplying or division factors, have infinite number of significant figure as per the condition.
Example:- In radius r = d/2 and circumference s = 2. has infinite number of significant figures.
7. The number of significant figure does not depend on the system of unit.
Example:- 16.4 cm, 0.164 m and 0.000164 km all have three significant figure.