In the AdWords learning center I took all the quizzes, if I did badly on a subject I reviewed the lesson.  Also when you got a quiz question wrong it would give you a good explanation of the right answer. 

You will need to study.  I would say even if you are an AdWords expert you would only get about half the question correct without studying.

The test itself:

90 minutes for 110 questions.

I would say at least 10 of the question did not make a whole lot sense. You have to read the question very carefully because I found several instances if I hadn’t re-read the question I would have gotten it wrong.

You have enough time to look up about 20 questions so if you think you can just look up all the answer that is not going to work for you.

I didn’t have any question on the following subject Google Analytics, Payments Outside the U.S., Account Types, Setup and Structure.