One of my teachers gives his students essay finals. First, he tells us three numbers, A, B, and C. He gives us A essay questions to study before the test. He picks B essay questions to put on the test, and we must pick out C of them to answer. He tells us to study A-B+C of the given questions if we want to pass the final.
As a procrastinator, I only studied the night before. Luckily, some other students had taken the test a day early, and could tell me which of the questions the teacher had picked. Of course, the teacher would pick a different combination of questions to give to the rest of the students. After hearing which questions were given, I realized I needed to study N less questions than was necessary before!
Find N, generalizing to all possible A, B, and C.
The question is rather ambiquous. From the question, it is difficult to tell whether questions A, B & C are related with each other. We could not tell from the question whether questions B that are tested are based on the information from question A. We also could not tell whether questions C that they have to pick up are related to the questions A & B. The questions also do not mention how many questions per each question. It may be there are ten questions from questions A. Fifty questions from question B. Or only one question in question C. Without the clear informations, it is difficult to determine one should study how many number of questions lesser in order to pass. The question also does not mention one has to pass the test by simply reaching the borderline pass. It could be that the question demands a question to gain a full pass with 100 marks that requires one to master all the questions. It could be that a person could tackle only one question & he could pass the test.
One should know that A might contain a number of questions instead of merely one. B might contain a number of questions that is different from A. For instance, there are 8 questions in A & 200 questions in B or C.
Let's assume that questions B are extracted from question A & that question C are extracted from question A too. On the assumption that previous questions would not be tested more than once by the teacher in each subsequent test, the text that he needs to study should be (A-B-c). For instance, if he needs to tackle only one question in order to pass the examination, it should be he needs to study one more question after studying 1/2 x (A-B-C) numbers of question.
Let's assume that A, B & C are different essays & there are not related with each other, he needs to study all in order to pass since the teacher can pick any one of them to test. If he wants to just pass the examination, he needs to study one more question after studying 1/2 of each of the questions, ie. A +B+C.
For instance, if the teacher sets a question in B, C & subsequent tests from the examples that are set from A & the teacher has the habit that the question he sets in B would appear in C & subsequent tests, he has to study the full questions A in order to pass all the questions.
Conclusion: As the question is rather a little ambiquous, it is difficult to jump into the conclusion to how many questions less that he has to study in order to pass. Not only that the word, pass, has not given with definition in the question. It could be just pass or 100% pass or as long as one could tackle one question he is considered to have passed.
No solution
