21/27 as a percentage is 77.78%. This value tells you how much of a whole the fraction represents when you look at it in terms of 100 parts.
The fraction 21/27 can be reduced to 7/9, which is a common way to see the same size in a simpler form. Whether you write it as 21/27, 7/9, or 77.78%, the amount stays the same.
Using the percentage makes it easy to compare with other numbers that are already in percent form, such as test scores or discount rates. It’s a quick way to see that the fraction is a little less than four‑fifths of a whole.
