Nowhere.
Fractions and decimals - in fact mathematics - are man-made concepts. They do not actually exist in physical form.
However, nowadays you would find it almost impossible to survive without their applications.
Chat with our AI personalities
Yes.
Any time we compare decimals, except in out dreams/nightmares! We cannot leave the real world purely for the purpose of comparing decimals and return to the real word when we have done that!
Money.
Irrational numbers are real numbers which cannot be expressed as fractions. In other words, decimals that never repeat. Examples: sqrt(2) -pi 4*sqrt(3)
To add fractions.