The practice exams are only intended to give you some idea about
 the average level of the questions.  In other words, passing the in
 class exams are more likely if you understand the solutions to the 
 practice questions. 
    Expect a few more difficult problems on the actual exams whose
 solutions are necessary for a grade of B or A.  The format of the 
 actual exams may be different.  There might be fewer or more
 questions, the actual exams may or may not be multiple choice.  
 Needless to say the practice exams are not a substitute for diligently
 doing the homework.