**Rounding Off:** The process of omitting the non significant digits and retaining only the desired number of significant-digits, incorporating the required modifications to the last significant digit is called rounding off the number.

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## Rounding Off – Units and Measurement

### Rounding Off – Definition, Rules

**Rules for Rounding Off a Measurement**

(i) If the digit to be dropped is less than 5, then the preceding digit is left unchanged, e.g. 1.54 is rounded off to 1.5.

(ii) If the digit to be dropped is greater than 5, then the preceding digit is raised by one. e.g. 2.49 is rounded off to 2.5.

(iii) If the digit to be dropped is 5 followed by digit other than zero, then the preceding digit is raised by one. e.g. 3.55 is rounded off to 3.6.

(iv) If the digit to be dropped is 5 or 5 followed by zeros, then the preceding digit is raised by one, if it is odd and left unchanged if it is even. e.g. 3.750 is rounded off to 3.8 and 4.650 is rounded off to 4.6.

**Units and Measurement Topics:
**Measurement requires tools to provide scientists with a quantity. A quantity describes how much of something there is and how many there are.

Physical Quantities and Their Units | Systems of Units |

Dimensions | Significant Figures |

Rounding off | Error |

Combinations of Errors |