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Rational Number

A rational number is one that can be written as the ratio of two integers.

See also Irrational Number

A rational number is one that can be represented as the ratio of two integers. For example all the numbers below are rational:

When expressed as a decimal number, rational numbers will sometimes have the last digit recurring indefinitely. For example with the last '3' digit recurring forever. See Decimal notation.

Word origin

In everyday use, the word 'rational' usually means logical, and following reason. If someone is acting irrationally, they are acting in an unpredictable and illogical way.

In mathematics, the word has a completely different meaning.  It comes from the the word 'ratio'. A rational number is one that can be written as the ratio of two integers. An irrational number is the opposite, one that cannot be written as a ratio of two integers.

Other number topics

Scalar numbers

Counting numbers

Numbers that have factors

Special values