An adaptation of the Catechism for Young Children in modern English.
Question: How many persons does this one God exist in?
Answer: This one God exists in three persons.
Question: In how many persons does this one God exist?
Answer: In three persons.
The preposition “in” is moved (in grammatical violation) to the end of the question for clarity and the answer is expanded to supply the full phrase “This one God exists in three persons”.