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Note: This item is one of a special case - **Known Unknowables**

An irrational number is a real number that cannot be expressed as a ratio of integers, i.e. as a fraction.

Examples are π, √2 etc.

For many irrational numbers, relatively simple mathematical proofs exist which show that it's impossible to ever arrive at finite solution.

(√2 was proved to be an irrational number by Greek mathematicians more than 2000 yrs ago).

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