355/355 = 100%
A fraction like 355/355 represents a complete amount, so it equals 100%. You might see this when all 355 students in a school turn in a permission form, or when every item on a checklist is finished.
You can picture it as one whole circle filled in completely, with no empty space left. A quick estimate is to notice that the numerator and denominator are the same, which means the fraction is the full amount.
A common mistake is thinking that 355/355 must be a very large value because the numbers are large. The size of the numbers does not matter here; because they match, the fraction still represents exactly one whole, or 100%.