This is the 3308th most frequent Chinese word.
四分之一
A quarter; one-fourth.
In this sentence, '四分之一' is used to represent a quarter portion of the unit 'an hour'.
一个小时的四分之一是十五分钟。
A quarter of an hour is fifteen minutes.
Here, '四分之一' indicates a fraction of the entirety, specifically a quarter of the whole cake.
你可以取蛋糕的四分之一来试吃。
You can take a quarter of the cake to taste.
In this example, '四分之一' is employed to describe a proportional part of a full unit, here 'a day', indicating the duration of exercise.