As an aside, if "he was playing Monopoly" is indeed the expected answer I would be hard pressed to think of a worse type of question to ask at an interview. Using deliberately misleading phrasing to turn a trivial question into a riddle is not clever or insightful; asking a question like that at an interview goes beyond merely irritating to bordering on insulting. See also: http://xkcd.com/169/

Might as well ask the interviewee "What have I got in my pocket?"