rational number
(another Prime Pages' Glossary entries)
The Prime Glossary
Glossary: Prime Pages: Top 5000: In mathematics rational means "ratio like." So a rational number is one that can be written as the ratio of two integers. For example 3=3/1, -17, and 2/3 are rational numbers.

Most real numbers (points on the number-line) are irrational (not rational). The rational numbers are those which have repeating decimal expansions (for example 1/11=0.09090909..., and 1=1.000000...=0.999999...). They are also those which have terminating continued fraction expansions. Finally, the real number x is rational if and only if there are finitely many solutions to |x - a/b| < 1/b2.

See Also: IrrationalNumber, AlgebraicNumber

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