Rounding Off the Digits
Rounding off a number is done to obtain its value with a definite number of significant figures.
For this following are the rules:
- If the digit to drop is less than 5, then the preceding digit is not changed.
For e.g., 1.24 is rounded off to 1.2.
- If the digit to drop is greater than 5. than the preceding digit is raised by 1.
For e.g., 19.48 is rounded off to 19.5.
- If the digit to drop is 5 and the preceding digit is even, then it is not changed.
For e.g., 1.25 is rounded off to 1.2.
- If the digit to drop is 5 and the preceding digit is odd, then it is increased by 1.
For e.g., 3.35 is rounded off to 3.4.
Example: Let’s round off 92.810576 to:
| (a) |
1 significant figure |
9 is the first non-zero digit, that means the first significant figure. In 92.810576 the second figure is 2 which is less than 5 so we round down the number to 90 |
| (b) |
3 significant figures |
In 92.810576, 928 are the first three digits, the next figure is 1 which is less than 5, so we round down given number to 3 sig. fig. = 92.8. |
| (c) |
6 significant figures |
In 92.810576, the first six significant numbers are 92.8105. The zeros between the figures are significant. The next figure 7 which is more than 5, so we round up number as = 92.8106 |
Example: Let’s round off 0.0046753 to:
| (a) |
1 significant figure |
figures in their correct places. In the above number the figure to the right of 4, is 6 which is more than 5, so we round up the number. When we round off 0.0046753 to 1 sig figures is = 0.005 |
| (b) |
2 significant figures |
When we round off 0.0046753 to 2 significant figure is 0.0047. |
| (c) |
4 significant figures |
In the above number, 5 is the 4th significant figure. The figure to the right of 5 is 3 which is less than 5, so we round down the number. When we round off this number |
