The following is a question from one of my example sheets, ie questions for the purpose of practising material covered in lectures:
You are given m apparently indentical coins, one of which may be a forgery. Forged coins are either too light or too heavy. You are also given a balance, on which you may place any of the coins you like. The coins placed in either pan may be together heavier or lighter than those in the other pan, or the pans may balance.
You are allowed at most 3 uses of the balance. Show that if m > 13 then you cannot be sure of detecting the forgery and its nature.
Sound familiar? Well, I'm not asking you to do my homework: your challenge is not to solve the problem above (which has already appeared in P+P more than any other problem, I suspect). Your challenge is to answer the following: what is the name of the lecture course for which the problem has been set? The metaphorical biscuit will go to the first guess that is sufficiently close to the answer. As a hint: you might find it helpful to look at one of my earlier posts on the RHP forums, in which I give a fairly thorough analysis of the balance problem, long before I started attending this particular lecture course.