10/28 as a percentage is 35.71%. This is the decimal form of the fraction turned into a percent and rounded to two decimal places.
The fraction 10/28 can be reduced to 5/14, which still represents the same part of a whole. Whether you write it as 10/28, 5/14, or 35.71%, the value stays the same.
Knowing the percentage makes it easier to compare with other numbers, like test scores or discounts. A value of about 36% tells you that the portion is a little more than one‑third of the whole.