Quant Brain Teasers & Logic Puzzles

Master 100+ brain teasers, probability questions, and logic puzzles used in quantitative trading interviews. Get step-by-step solutions and practice with problems from Jane Street, Citadel, Two Sigma, and other top firms.

Logic Puzzles

Classic logic puzzles and reasoning problems commonly asked in quant interviews.

50+ ProblemsStep-by-step solutions
Probability

Probability and statistics problems with detailed explanations and calculations.

30+ ProblemsReal interview questions
Finance

Market-making problems, arbitrage opportunities, and trading scenarios.

25+ ProblemsIndustry-specific
Math

Advanced mathematical problems and computational challenges.

20+ ProblemsComplex calculations

Featured Brain Teasers

Weighing Coins II
Reasoning

You have 12 coins, one of which is counterfeit. Using only a balance scale, find the counterfeit coin in exactly 3 weighings.

Hard
Index Dynamics: DAX
Finance

Calculate the expected return of a DAX index strategy given market volatility and correlation assumptions.

Medium
Julia's Children
Probability

Julia has two children. If at least one is a boy born on Tuesday, what's the probability both are boys?

Easy
Consecutive Sixes
Math

What's the probability of rolling two consecutive sixes when rolling a die until you get two consecutive sixes?

Medium
Hourglasses
Reasoning

You have two hourglasses: one measures 7 minutes, another measures 4 minutes. How do you measure exactly 9 minutes?

Easy
ETF Arbitrage
Finance

An ETF is trading at $102, but its NAV is $100. What arbitrage opportunity exists and how would you execute it?

Medium

Step-by-Step Solutions

Example: Hourglasses Problem
How to measure exactly 9 minutes with 7-minute and 4-minute hourglasses

Step 1: Start Both Hourglasses

Start both hourglasses simultaneously at time 0.

Step 2: Flip 4-minute Hourglass

At time 4 minutes, the 4-minute hourglass finishes. Flip it immediately.

Step 3: Flip 7-minute Hourglass

At time 7 minutes, the 7-minute hourglass finishes. Flip the 4-minute hourglass again.

Step 4: Calculate Total Time

At time 9 minutes (7 + 2), the 4-minute hourglass will finish again. Total time = 9 minutes.

Firm-Specific Brain Teasers

Jane Street Problems
Probability and market-making questions
  • • Coin flipping probability
  • • Market making scenarios
  • • Expected value calculations
  • • Risk management problems
Citadel Problems
Advanced mathematical challenges
  • • Complex probability trees
  • • Statistical inference
  • • Optimization problems
  • • Algorithm design
Two Sigma Problems
Data science and machine learning
  • • Data analysis puzzles
  • • Pattern recognition
  • • Statistical modeling
  • • Algorithm complexity

Frequently Asked Questions

What types of brain teasers are asked in quant interviews?

Quant interviews typically include logic puzzles, probability problems, market-making scenarios, and mathematical challenges. Common topics include coin flipping, dice problems, optimization, and statistical reasoning.

How should I approach brain teasers in interviews?

Start by understanding the problem clearly, ask clarifying questions, think out loud, break down complex problems into smaller parts, and always explain your reasoning process. Interviewers care more about your thought process than getting the exact answer.

Are there common patterns in quant brain teasers?

Yes! Many brain teasers follow similar patterns: probability calculations, optimization problems, logical reasoning, and mathematical proofs. Understanding these patterns helps you solve new problems more efficiently.

Master Quant Brain Teasers Today
Practice with 100+ brain teasers, get step-by-step solutions, and ace your quantitative trading interviews.