The 47 classic quant interview questions

Every trading interview draws on the same small canon of famous problems. Monty Hall, the 25 horses, two eggs and a hundred floors, the prisoners and their boxes. They recur because each one has a trick worth testing: a symmetry to spot, an invariant to find, a piece of information that looks decisive and is not.

All of them are collected here, every one worked step by step, with the follow-up questions an interviewer asks once you land the answer. Free to read, no account needed. If you can do these cold, you have cleared the folklore and the real work starts in the full bank.