4/45 as a percentage is 8.89%. This number tells you how much of a whole 4 parts out of 45 represent when you look at it in terms of hundredths.
The fraction 4/45 is a small part of a whole, and it can be useful when comparing parts of a group. For example, if you have 45 items and you take 4 of them, you are taking about nine hundredths of the total.
Remember that the percentage form 8.89% gives a quick way to see the size of the fraction in everyday language, such as when you see discounts, statistics, or test scores.