Rules of Rounding Off Significant Figures
1. If the digit to be dropped in a number is less than 5, then the preceding digit remains unchanged.
Example : 1.54 is rounded off to 1.5 , 8.64 is rounded off to 8.6.
2. If the digit to be dropped in a number is equal or greater than 5, then the preceding digit is raised by one.
Example : 2.49 is rounded off to 2.5 , 8.66 is rounded off to 8.7.
3. If the digit to be dropped is 5 or 5 followed by zero, then the preceding digit remains unchanged if it is even
Example : 3.65 is rounded off to 3.6 , 8.650 is rounded off to 8.6.
4. If the digit to be dropped in a number is 5 or 5 followed by zeros, then the preceding digit is raised by one, if it is odd.
Example : 3.750 is rounded off to 3.8 , 8.750 is rounded off to 8.8 , 6.55 is rounded off to 6.6