66/91 as a percentage is 72.53%. This number tells you how much of a whole 66 parts out of 91 represent when you look at it on a scale of 100.
The fraction 66/91 can be thought of as taking 66 pieces from a set of 91 equal pieces. When you compare that to a full set of 100 pieces, you end up with about 72 and a half pieces, which is why the percentage is close to 73%.
Because the result is rounded to two decimal places, the exact value might be a tiny bit higher or lower, but for most everyday uses, 72.53% is the clear and convenient figure to work with.
