Lets says theres a question bank of 28 questions. On the exam, there will be 12 of these questions, and I will have to answer 5.
If the only way to get a question right is to study it, how many questions should I study to have a reasonable chance of knowing 5 answers?
More generally, how could I find out my expected score as a function of how many questions I study?
Obviously if I study 21, then I will get 100%, and if I study less than 5, I'm guaranteed to not get at least 5.