Exam Review #27: Why we use sig figs

  Why do we use significant figures?

There is a reason for sig figs! Sig figs are used to represent how accurate the previous measurements are. You cannot do calculations with measurements that are less precise than the measuring device actually used.  For example, if you were to use a ruler that measured to 1 decimal place (10 ticks between each inch mark), your measurement would have one decimal place determined by the scale and one decimal place that you estimated.  Estimations are necessary because whether you estimate or not, there will still be error.  Estimating provides less error than if you did not estimate.  When using the numbers in calculations, you cannot have more decimal places than were in the original measurement for addition and subtraction.  For multiplication and division, it depends on the lowest number of sig figs used (the least accurate measurement measured with the least accurate device).