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Definition: The comparison when two (or more) numbers are compared by division. Ratios are generally written as a:b or a/b. The ratio "a:b" is read "a is to b." The number that comes after the "to" goes second or at the bottom of the fraction.
Source: "Average". Visual Mathematics Dictionary. Edu2000 America Inc, 1995 - 2007. Web. 31 July 2012.