Significant Figures Index

Introduction

     We use specific number of digits to denote an exact value of a number for required accuracy. The digits used for such a purpose are called significant figures.

Significant Figures and Measuring Instruments

     The number of significant figures depends on the instrument used and accuracy required.

     It is wrong to record diameter as 2 cm. It means the reading is approximated to the nearest 1 cm. If the exact reading is 2 cm then it should be recorded as 2.0 cm.

     The significant figures express number of units, rounded to the nearest such unit.

Approximation

     We know that the digits of a number, one by one in order from left to right decrease in value rapidly.

     Numbers can be rounded off to any given place.

     When we round off a number to any given place we get an approximate value of the number.

Absolute Error and Percentage Relative Error

     The difference between these two values is called the absolute error.
Absolute Error = Original number - Approximated number
The ratio of the absolute error and the original number expressed in percentage form is called percentage relative error.

Summary

     1. We use specific number of digits to denote the value of a number to a certain degree of accuracy.

     2. For a number between 0 and 1, the successive zeros after the decimal are not significant.

     3. For a number with a decimal point, the final zeros are significant.