Fractions!  Yes, whether it be ratios, proportions, or the use of scale, the threat of fractions is an ever present danger.  Converting units of measure, in the previous section, may have already persuaded you of a tactical need for (conversion) fractions.  In this section, we explore some additional uses for fractions. In doing so, we still strive to concentrate on the relatively common and everyday applications while only on occasion do we stray into more esoteric phenomena.  What could so constitute "common and everyday uses?"  Let's start with the simple notion that a ratio is actually little more than a fraction.  Ratios may be written in different formats, such as a to b, a:b, or  a / b.  Mathematically speaking, it is almost always more practical to use the latter (a / b) form.  One of our more casual encounters with ratios are those disguised as rates.  For example, a speed of 30 mph (miles per hour) no doubt seems a fairly familiar concept.  Similar ratios (rates) abound in most everyone's daily experience, frequently expressed in the form of "a per b".