**Question (iii): Explain “rounding off” of numbers in scientific calculation.**

**Answer**

## Rules of rounding off a number

Rounding off of numbers is the method by which we reduce the long numbers in the calculation to the desired extent. Following are the rules for rounding off numbers in calculation.

- If the first digit to be dropped is less than 5, then that digit and all the digits to follow are dropped and the retaining digits are kept as it is.
- If the first dropping digit is greater than 5, the last retaining digit is increased in value by 1.
- When the first dropping digit is 5 then the following situation may arise;

(i) There is no non-zero digit after the dropping 5 like 12.345 or 32.33500.

In such a case, if the last retaining digit is even then 5 and the following digits are dropped and the number is kept as it is. If it is odd, the last retaining digit is increased in value by one unit.

(ii) There is non-zero digit/s at any position after the dropping 5. In such a case, 5 and the following digits are dropped and 1 is added to the last retained digit (no matter whether even or odd).