Rules for rounding off the data

Question: Briefly, describe rules for rounding off the data?

Rules for rounding off the data:

1. If the first digit dropped is less than 5, the last digit retained should remain unchanged.
2. If the first digit dropped is more than 5, the digit to be retained is increased by one.
3. If the digit to be dropped is 5, the previous digit which is to be retained is increased by one if it is odd and retained as such if it is even.
For example, the following numbers are rounded off to three significant figures as follows -The digits are deleted one by one
43.75              is rounded off as                 43.8
56.8546          is founded off as                 56.8
73.650            is rounded off, as                 73.6
64.350            is rounded off as                  64.4
4. In adding or subtracting numbers, the number of decimal places retained in the answer should equal the smallest number of decimal places in any of the quantities being, added or subtracted. In this case, the number of significant figures is not important. It is the position of decimal that matters.
For example, suppose we wish to add the following quantities expressed in meters.
 72.1 2.7543 3.42 4.10 0.003 1.273 75.523 8.1273 75.5 m 8.13 rn

Correct answer:    75.5 m                            8.13 rn

In case (I) the number 72.1 has the smallest number of decimal ‘places, thus answer is rounded off to the same position which is then 75.5 m
In case (ii) the number 4.10 has the smallest number of decimal places and hence the answer is rounded off to the same decimal positions which is then 8.13m.