# Rational number

A **rational number** is any **number** that can be expressed as the quotient or **fraction** (a/b) of two integers, with the denominator not equal to zero. Any rational number with a **denominator** whose only prime factors are 2 or 5 may be precisely expressed as a **decimal fraction**.

Example:

1/2=0.5

1/20=0.05

1/5=0.2

1/4=0.25

1/25=0.04

But if the **rational numbers** denominator has any prime factors other than 2 or 5, decimal fraction cannot be expressed as finite decimal expansion, and has a unique eventually repeating infinite decimal expansion.

Example:

1/3=0.333333… (with 3 repeating)

1/9=0.111111… (with 1 repeating)