The NAPLEX questions seemed a little more difficult for me while I was taking the test than the quiz bank questions, but that's probably because taking the actual exam is more stressful than answering quiz questions online on your own time. The types of questions and the way they are formatted on the quiz bank was quite similar to the NAPLEX. For example, I had some "check all that apply" questions, as well as math calcs where I had to type in my own answer (as opposed to multiple choice) and questions where I had to identify the site of action of a drug on a graphic image. In regards to the structure of the questions, the biggest difference was that I did not have ANY questions where "all of the above," "none of the above," "A and B only," etc. were possible answers, yet the quiz bank had many of those questions.
Reference values for lab results were always provided on my exam. Equations, however, typically were not - the only equations that I needed were creatinine clearance and adjusted phenytoin level for low albumin. I was asked to calculate a patient's basal energy expenditure, but the calculation was provided in that case. Of course, there are many possible questions that could be asked, so I would review equations prior to the exam, knowing that they are generally not provided. I believe I had one question where I had to recognize that the patient's valproic acid level was elevated, but other than that, I wasn't asked about normal serum levels for drugs.
My very first question was a calculation, so I anticipated that it would be a lot of math. If I had to guess, I'd say that my exam was probably ~30% calculations. I had multiple questions that involved calculating flow rates, and I also had quite a few problems asking me to calculate the amount (or percentage) of calories a patient will receive from one TPN component in a 24-hour period. There were also several types of calculations that I was expecting to encounter on the exam that I did not receive (osmolarity, mEq, aliquots, alligations, and so on). The calculations were the one part of my exam that were easier than I expected, so yes, I thought RxPrep adequately prepared me for that portion.
