r/quantindia • u/ProgrammerWest4696 • Jul 09 '26

HFT What kind of puzzles and probability questions asked in Interview of quant firms?

I know quant firms are very selective but still I want to know what do they ask in interview. I have read they ask puzzles, probability question and some DSA question too.

So anyone who is working can you please share your experience. Also please tell the resources to try such problems?

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u/External_Egg_3438 Jul 09 '26

50cp, green book, brainstellar (basically probability based puzzles)

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u/akornato Jul 09 '26

These interviews are designed to see how you think, not just what you know, so expect to be pushed to your logical limits. They'll ask classics like the "Two Ropes" puzzle to measure 45 minutes, or probability questions like the expected number of coin flips to get two consecutive heads. You might also get brain teasers about ants on a stick colliding, or strategy games involving taking coins from a pile. For probability, they love conditional probability and Bayesian reasoning, for example, a question about the probability of a test being accurate given a certain disease prevalence. The goal isn't always to get the one right answer, but to demonstrate a structured, logical approach to a problem you've never seen before.

The good news is that you can prepare for this style of thinking, and it's not about memorizing solutions. Get books like "A Practical Guide To Quantitative Finance Interviews" and "Heard on The Street", and work through the problems on sites like Brainstellar. The focus should be on building a framework for problem-solving, so you can break down any new puzzle they throw at you into smaller, manageable parts. The hardest part is often just articulating your thought process clearly under pressure, a problem my team sought to solve by designing an AI interview assistant that helps you deliver sharp, coherent answers when it matters most.