Question

The recipe called for one-third of a cup of flour, but I accidentally put in three cups.

Why does one-third contain a hyphen in this sentence? I need the answer pls

Answer 1

It contains a hyphen so you know the two words are connected and so you don't make the mistake of putting 3 cups in instead of 1/3

Answer 2

Answer: fractions are hyphenated when used as adjectives.