Blog
Mental math, trading interviews, and quantitative test prep.
Citadel Interview Prep: Quant, Trading, and Research Roles
How to prepare for Citadel's notoriously rigorous interview process — covering the math tests, probability questions, brainteasers, and trading simulations that screen for elite candidates.
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Jane Street Interview Prep: Mental Math, Probability, and the Trader Game
Jane Street's interview process is among the most rigorous in finance. Here's what to expect and how to prepare for the mental math, probability, and trading game rounds.
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Two Sigma Interview Prep: Quantitative Research and Software Engineering
How to prepare for Two Sigma's data-driven interview process — covering the coding challenges, statistics problems, research case studies, and the quantitative mindset they're looking for.
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Expected Value: The Complete Guide for Quant Interviews and Trading
Master expected value from first principles — the math, the intuition, the Kelly criterion, and the 20 classic EV problems that appear in every quant interview.
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Prop Firm Quantitative Tests: Complete Guide (Optiver, SIG, Jane Street, Citadel)
A comprehensive breakdown of the mental math and quantitative screens used by the major prop trading firms — what each firm tests, how hard the screens are, and exactly how to pass.
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HRT Interview Prep: Hudson River Trading Quantitative Roles
How to prepare for Hudson River Trading's notoriously rigorous interview process — covering the math, probability, algorithms, and the HRT mindset they're screening for.
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SIG (Susquehanna) Interview Prep: Math, Probability, and Poker Thinking
Susquehanna International Group's interview process tests mental math, probability, and game-theoretic reasoning. Here's what to expect and how to prepare.
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Bayes' Theorem for Traders: Updating Beliefs in Real Time
How Bayesian reasoning underpins prop firm interviews, trading decisions, and quantitative research — with 12 worked problems and the mental model every quant must have.
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50 Fermi Estimation Practice Problems with Solutions
50 Fermi estimation problems across markets, science, and everyday life — each with a worked solution showing the chain of reasoning that makes it tractable.
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100 Quant Trading Interview Questions (with Answers)
The definitive list of 100 quantitative trading interview questions — covering mental math, probability, expected value, markets, and brainteasers — each with a complete answer.
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30 Probability Interview Questions with Solutions (Quant & Prop Firm)
The 30 probability questions that appear most often in quant trading and prop firm interviews — each with a complete worked solution and the concept it tests.
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D.E. Shaw Interview Prep: Quant Research and Software Engineering
How to prepare for D.E. Shaw's demanding interview process — covering the quantitative puzzles, systems thinking, coding challenges, and the intellectual culture they screen for.
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Mental Math Tricks Every Trader Should Know
The arithmetic shortcuts that let professional traders calculate faster than a calculator — and how to build these reflexes through deliberate practice.
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How to Build Market Intuition: A Trader's Guide to Price Sense
Market intuition isn't innate — it's calibrated through deliberate practice. Here's how professional traders build the mental models that let them sense when prices are wrong.
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Statistics for Quant Interviews: The Complete Prep Guide
Master the statistics concepts that appear in every quant trading interview — hypothesis testing, distributions, regression, and the statistical reasoning that separates good candidates from great ones.
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Prop Firm and Quant Finance Compensation Guide 2025
What quant traders, researchers, and engineers actually earn at Optiver, Jane Street, Citadel, Two Sigma, D.E. Shaw, and HRT — including base, bonus, and total comp ranges.
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How to Study for Quant Trading Interviews: The 12-Week Plan
A week-by-week study plan for prop firm and quant trading interviews — what to study, in what order, how to practice, and how to know you're ready.
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What Is Fermi Estimation? A Beginner's Guide with Examples
Fermi estimation is the skill of making accurate order-of-magnitude estimates from first principles. Here's what it is, why traders and quants use it, and how to practice it.
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25 Quant Trading Brainteasers with Complete Solutions
The 25 classic brainteasers that appear most often in prop firm and quant hedge fund interviews — each with a complete solution and the reasoning pattern it tests.
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How to Build Mental Math Speed: The Training Protocol
A systematic training protocol to build the mental arithmetic speed required for Optiver's 80-in-8 test and other prop firm assessments — including daily drills, technique progression, and benchmark targets.
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How to Prepare for the Optiver Mental Math Test
The Optiver mental math test (80 questions in 8 minutes) is one of the most demanding arithmetic screens in finance. Here's how to prepare systematically.
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Prop Firm Interview Process: What to Expect at Every Stage
A complete walkthrough of the prop firm interview process — from online assessments through superday — with timelines, what each stage tests, and how to prepare for each round.
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Order of Magnitude Thinking: The Trader's Framework
How to develop order-of-magnitude intuition — the ability to instantly judge whether a number is plausible, implausible, or wildly wrong — with the frameworks and anchors every quant needs.
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Fermi Estimation in Trading Interviews: What They're Actually Testing
Why hedge funds and prop firms use Fermi estimation questions, what skills they're measuring, and how to build a systematic approach.
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Mental Math Shortcuts for GMAT and GRE Quantitative Sections
The GMAT and GRE reward fast mental arithmetic. These shortcuts let you skip the calculator and solve in your head — faster and more accurately.
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Practice what you read
Build the skills from each guide with daily drills.