AFAIK, Microsoft certification exams use "adaptive" questions so there is no
set number of questions you have to answer. The level of difficulty of a
question depends on how well you answered previous questions (higher level
of difficulty if you do well). The exam software basically assesses your
knowledge as you go and once it can decide on your knowledge it will pass
(or fail) you. So basically, if you answer 10 questions perfectly, it can
assess you as competent and pass you.
BTW, you posted in the wrong newsgroup. This newsgroup is for Microsoft
Access (a database application). Suggest you post to one of the certication
newsgroups or check Microsoft Web site on "certification".