2. Getting Started
2.1 Exact Numbers
Before we launch into all the finer points of dealing with significant figures, I should mention that my statement above that nothing in life is perfect isn't quite true. There arenumbers which are known exactly, and these come into significant figure calculations quite often. As an example, count your ears. Most people have two. How much do we trust this number? Well, we know that we have exactlytwo ears, and that we are surethat we have that many and no more or less (unless, of course, our parents spent too much time touring the uranium enrichment plant before we were born, in which case there might be some doubt as to the exact number of ears we dohave...). We can therefore place infinite confidence in this number, and as a result we say that this number is infinitely accurate. In fact, all such counting numbers are infinitely accurate. This is an important point and will be dealt with again in a later section. Let's drop it for the moment, though, and move on to numbers which are inexact.
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