57/78 as a percentage is 73.08%. This tells you how much of a whole the fraction represents when you look at it on a scale of 100.
The fraction 57/78 can be reduced to 19/26, but it still points to the same part of a whole. Whether you write it as a fraction or a percentage, the value stays the same.
Seeing the percentage makes it easier to compare with other numbers, like test scores or discounts. If something is 73.08% of a total, you know it’s a little more than three‑quarters of that total.
