Use of Three Significant Digits

It is possible to become thoroughly confused about how many significant figures to retain in an answer. In such a case, it is of ten pmnissible to use 3 significant figures. 

Generally, this gives sufficient accuracy without doing grievous harm to file concept of significant figures. 

The development of chemistry has depended strongly upon careful measurements. Historically, measurements of the quantities of substances reacting and produced in chemical reactions have allowed the explanation of the fundamental nature of chemistry. Exact measurements continue to be of the utmost importance in chemistry, and are facilitated by increasingly more sophisticated instrumentation. For example, atmospheric chemists can determine a small degree of stratospheric ozone depletion by measuring minute amounts of ultraviolet radiation absorbed by ozone with satellite-mounted instruments. Determinations of a part per trillion or less of a toxic substance in water may serve to trace the source of a hazardous pollutant. This section discusses the basic measurements commonly made in chemistry and environmental chemistry. 

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