What are Significant Figures?

 

SIGNIFICANT FIGURES:

              There are two types of values, exact and measured. Exact values are those that are counted clearly. For example, while reporting 3 pencils or 2 books, we can indicate the exact number of these items.

                                On the other hand, values associated with measurements of any kind are uncertain to some extent. For example,  if we want to measure the length of a pencil with an ordinary meter ruler having a least count of 1mm and we note that the length of the pencil is greater than 67 mm and less than 68 mm. We can estimate that the length of the pencil is 67.5 mm. This length is accurate in mm up to 67, but the last fraction of mm has been guessed. There is a chance of error in the last figure. It is known as the doubtful figure.

                           The number of accurately known figures and the first doubtful figure are known as significant figures.