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# Rational numbers

A rational number, or fraction, is any number that can be written as the ratio of two integers.

$2$, $-2/5$ and $3.1$ are rational numbers. $3.1$ is a rational number because it can be written as the ratio $31/10$.

All integers are rational numbers. For example, $5$ can be written as the ratio $5/1$.

Examples of numbers that are not rational are $\sqrt{2}$, $\pi$, or the cube root of $2$.

The symbol for the set of the rational numbers is $\mathbb{Q}$.

Basic operations on rational numbers (addition, subtraction, multiplication and division) always give a rational number.

All integers are rational numbers.