In English, one way to respond to a question where the answer is obviously yes is to ask back "Is the Pope Catholic?" What is a Russian analogue, i.e., a conventional question-as-reply for which the answer is clearly affirmative?
A good answer to this question should work, for instance, in both of the following situations:
1) Replying to "I saw Ivan on the bus to the airport. Is he traveling somewhere?"
2) You are a chemist and someone says to you "There is a username on chemistry.stackexchange that is your first initial and last name. Is that you?"