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# Irrational Number

An irrational number is a real number that cannot be written as a fraction. Irrational numbers have decimal expansions that neither terminate nor become periodic.

Irrational number is a middle school-level concept. It is listed in the California State Standards for Grade 7.

### Examples

 Golden Ratio: The golden ratio φ is a mathematical constant obtained as the ratio of longest-to-shorted side lengths in a rectangle constructed so that when it is partitioned into a square and new rectangle, the new rectangle has the same ratio of side lengths as the original. The golden ratio has value of approximately 1.618. Pi: Pi is the mathematical constant defined as the ratio of the circumference of a circle to its diameter with value of approximately 3.14159. e: The mathematical constant denoted e is the base of the natural logarithm which has value of approximately 2.718.

### Prerequisites

 Fraction: A fraction is a rational number expressed in the form a/b, where a is known as the numerator and b as the denominator. Rational Number: A rational number is a real number that can be written as a quotient of two integers.