For example the fraction 2/4 is equal to 1/2 and therefore not irreducible, but the fractions 1/4, 5/6 and -101/100 are irreducible.

It can be shown that a fraction *a*/*b* is irreducible if, and only if, *a* and *b* are coprime.

A fraction that is not irreducible can be reduced by using the Euclid's algorithm to find the greatest common divisor of the numerator and the denominator, and then dividing both the numerator and the denominator by the greatest common divisor.