Which preposition to use with centage

of Occurrences 4%

Bark will do it, which accounts for the fact that the blood of dogs has a large per centage of iron.

after Occurrences 1%

"You may die at any moment, and probably will," concluded Mr. SCHENCK, thoughtfully; "but still, on the score of friendship, we'll give you a Policy for a reasonable amount, and take the chance of being able to compromise with your mother on a certain per centage after the funeral.

Which preposition to use with  centage