A case interview normally lasts anywhere from 15 to 20 minutes. Essentially it is a single question that introduces you to a hypothetical dilemma that is being faced by a particular company. You will need to use your analytical and problem-solving skills to devise a possible solution to the problem. The firm that is interviewing you wants to make sure that you have the ability to apply your knowledge to a real world situation. It is important that you can think quickly on your feet and generate well-rounded ideas.
