# What are significant figures.

Hey fellows I have read a number of books on Significant figures but I am not able to understand what are these. One confusing thing is that eg. If I take length of wire with a meter rod (with 1 meter minimum length measureable) & found it to be 7 meters. Then according to rule of Significant figure there must be some error in measurement & measurement must be within 6-8 meters. Please someone give explanation of this.

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LowlyPion
Homework Helper
Welcome to PF.

The issue is more in the expression of the length than in the meter stick you are using. While the finest scale may be 1 meter in your example, the observer may reasonably estimate to say 1/4 of that and your uncertainty could be expressed as ± 1/4 if more % precision is useful.

On the other hand if you have a measure that is 1000 m long, and it is only marked, in 1 m increments, then a ± 1 m may be satisfactory precision for the kinds of measurements you would be making.

In other words, I think some common sense needs to used in actual practice.

minger