How to Prepare for Quant Trading Interviews: Probability, Mental Math and Thinking Out Loud

Quant trading interviews have a reputation for being some of the hardest in any industry. Firms such as market makers and proprietary trading shops receive thousands of applications for a handful of graduate and internship seats, and their process is designed to find people who can reason quickly and clearly under pressure. The good news is that the format is fairly predictable. If you understand what each stage tests, you can prepare in a focused way instead of trying to learn everything. 1. The online assessment Most processes start with timed tests: mental arithmetic, number sequences, probability multiple choice and sometimes a short coding task. Speed matters as much as accuracy. Practise mental math every day for a few weeks rather than cramming. Get comfortable with fractions, percentages, multiplying two-digit numbers and quick estimation. The aim is not to become a human calculator. The aim is to stop arithmetic from using up the attention you need for the actual problem. 2. Probability and expected value The first live interviews usually include probability puzzles: dice games, card draws, coin flips, conditional probability and expected value questions. A classic example is "You roll a die and get paid the number shown, but you may re-roll once. What is the game worth?" Interviewers care less about a memorised answer than about how you set up the problem. Define the outcomes, write down what you know and explain each step. If you make a mistake and catch it yourself, that often counts in your favour. Good preparation material includes the well-known "green book" style puzzle collections, past questions shared by candidates and simple simulations you write yourself in Python to check intuition. 3. Market making games Many trading firms run a market making exercise. You are asked to quote a bid and an offer on an unknown quantity, for example the sum of three cards, and the interviewer trades against you. The skill being tested is updating your estimate as new information arrives and managing risk instead of trying to be right on every trade. Keep your spreads sensible, adjust after each trade, and say out loud why you are moving your quotes. 4. Behavioural and fit questions Candidates often neglect this part. Expect questions like "Why trading rather than software or research?", "Tell me about a decision you made with incomplete information" and "Describe a game or competition you take seriously." Firms want people who are comfortable with uncertainty, accept losses calmly and work well in small teams. Prepare two or three short stories that show this, ideally with numbers. 5. Thinking out loud under pressure The most common reason strong candidates fail is not a lack of knowledge. They go quiet. Interviewers can only score what they hear, so practise explaining your reasoning as you go, even on problems you find easy. Mock interviews with friends help a lot, and so does recording yourself solving puzzles. Tools can help here too. Linkjob AI (https://linkjob.ai) provides real-time help during live job interviews and technical interviews. It can prompt you with structure when your mind goes blank, which is useful for candidates who know the material but freeze in the moment. Use it as a support for clear thinking, not a replacement for practice. 6. A simple four-week plan Week 1: daily mental math drills plus basic probability review. Week 2: 10 to 15 probability and expected value puzzles a day, solved out loud. Week 3: market making practice with a friend, plus your behavioural stories. Week 4: full mock interviews, timed online tests and rest before the real thing. Quant trading interviews are tough, and luck plays a part. Many well-prepared candidates still miss out in a given year. But steady preparation that focuses on clear reasoning, calm risk-taking and good communication gives you the best chance, and those skills carry over to every other technical interview you will face.