Brain Teasers quant interview questions

Brain teasers remain part of many quant trading interviews because they reveal how you think when there is no formula to reach for. Typical problems involve logic puzzles, weighing and switching problems, clever invariants, estimation questions and games where you must find a winning strategy. Interviewers care less about the final answer than about a structured approach: simplify, try small cases, look for symmetry and explain your reasoning clearly. This collection groups classic-style teasers written as original QuantSolve problems, from quick warm-ups to multi-step puzzles. Each free problem has hints that nudge rather than spoil, plus a clean worked solution. Practising them builds the calm, systematic habits that also help with probability, expected value and market making questions under pressure.