How does it matter?
It is impossible to know the exact number of questions you need to correctly answer to pass since there are so many variables and weightages depending on degree of dificulty of a particular question.
Even if you knew the exact number, what will you do? Prepare so that you can get the minimum number of questions right or stop answering questions once you have reached the desired number on the test?
Personally I believe in the saying "prepare for the worst, hope for the best"