How many totall questions in exam 70-646? what is the maximum time limit?
Without breaking the NDA:
If you're asking how many questions are in the question pool for the exams... Only MS knows.
If you're asking how many questions are in the exam that you'll sit... There's no fixed answers, as normally it's a range between 40-50 questions.
As for the time limit, I believe it's 125 minutes (plus survey time which doesn't apply to the exam questions). So just over two hours, but this will be confirmed when you book thru Prometric.
Hope this helps :)
-Ken | http://ken.wagnerfamily.co.uk