90/91 as a percentage is 98.90%. This is the rounded value you get when you change the fraction into a percent and keep two decimal places.
The fraction 90/91 is very close to the whole number 1, which means it represents a number just a little bit less than 100%. When we look at it in everyday terms, you can think of it as almost a complete whole.
Because the exact decimal is a long string of numbers, we round it to make it easier to read. Rounding to two decimal places gives us the neat figure 98.90%, which is simple to use in reports or calculations.
In most practical situations, using 98.90% works well enough. It tells you that the fraction is almost perfect, missing just a tiny bit from being a full 100%.
