How to prepare for a quant trading interview

The hiring pipeline

Most quant trading firms, including Optiver, IMC, Jane Street, Flow Traders, SIG (Susquehanna International Group), Akuna, CTC (Chicago Trading Company), Maven, and market makers such as Citadel Securities, run a version of the same funnel: an online screen, one or two interview rounds, then a final round often called a superday.

Stage one is a timed online assessment on a third-party platform or a firm-built tool. It usually combines a mental math speed test with a numerical or logical reasoning section and, increasingly, a short gamified module that scores traits such as decision-making under uncertainty. If you pass, the next step is usually a 30-60 minute phone or video interview: a few probability or expected-value problems, sometimes a quick math re-check, and a couple of fit questions.

The superday is several back-to-back interviews of about 30-45 minutes each. They cover probability and brain teasers, a trading or market-making game, technical or coding rounds (more of these for research and developer-adjacent roles), and behavioral fit, which is sometimes assessed inside the other sessions. Round count, timing, and structure vary by firm and year. From first assessment to offer usually takes several weeks, and can be faster during graduate recruiting cycles.

The mental math speed test

Optiver's "80-in-8" (80 arithmetic questions in 8 minutes, no calculator) is the most publicly documented version of this test and the one most candidates benchmark against first. Flow Traders, SIG, Akuna, and Maven run their own timed numerical tests, and CTC's mixed-reasoning OA includes a numerical section. Question count, length, and format vary by firm and year, and some split arithmetic from a separate pattern-recognition or sequence section.

The content is basic arithmetic: two- and three-digit multiplication and division, percentage changes, fraction-to-decimal conversions, quick compounding, and converting between odds and implied probability. There is no calculus. The test measures fast, low-error arithmetic under time pressure, which is what adjusting quotes on a fast-moving order book requires.

There is no credit for showing your work, so the test rewards recall speed more than derivation. The most useful prep is making things you already know (17% of 640, 13 × 24, 5/8 as a decimal) automatic. Firms use these scores as a cheap filter before spending interviewer time.

Free timed practice (no signup): Optiver-style 80 in 8 simulator · Flow Traders math test · SIG-style speed test · Maven Securities math test.

How negative marking changes strategy

Most mental math speed tests penalize wrong answers while a skipped question costs nothing. The penalty differs by format: Optiver-style 80-in-8 is reported as −1 per miss against +1 per hit, and the Flow-style format as −2. Treating the test like a school exam is the most common strategic mistake candidates make.

The penalty sets the break-even. At −1, a guess has to be right more than half the time to gain points on average. At −2, it has to be right more than two-thirds of the time (about 67%), and even a 50/50 guess between two options loses 0.5 points on average. Skipping scores zero; a guess with no basis usually has negative EV. So triage each question within a couple of seconds: solve now, skip, or answer when your confidence clears the break-even. Under all of these scoring schemes, 70 attempts at 90% accuracy score higher than 80 attempts at 75%.

Train two separate skills: calculation speed, and a quick, honest read of your own confidence. Candidates who only practice speed tend to lose accuracy under test conditions.

Brain teasers and probability rounds

After the numerical screen, interviews move from arithmetic to reasoning: expected-value problems (pricing a bet, valuing a game with uneven payouts), conditional probability and Bayesian updating, combinatorics, and Fermi estimation. Classic logic riddles still appear, but less often than probability and EV questions.

Interviewers usually know the answer already and grade how you reach it: whether you state assumptions out loud, define variables before computing, split a messy problem into smaller pieces, and sanity-check the size of your result. Many will push back on a correct answer or change the problem halfway through to see whether you can adapt your reasoning without freezing or defending a memorized approach.

Memorized answers to famous brain teasers rarely help, because interviewers vary the setup. Practice the underlying tools (expected value, Bayes' rule, combinatorics, structured estimation) so they apply to whatever puzzle you get.

Worked examples: quant interview brain teasers · sequences & probability speed test.

Trading games and market-making simulations

Many superdays include a live trading or market-making game, one-on-one with an interviewer or in a group. You get partial information (your own cards, a news feed, or asymmetric signals) and have to quote a bid/ask spread, trade, and manage a position as new information arrives.

Interviewers look at whether your spread width reflects your uncertainty (wide when unsure, tight when confident), whether you update your fair-value estimate correctly, whether you manage position size and risk, and how you respond when a better-informed counterparty picks you off, which is an unavoidable part of market making. Composure after a bad trade counts as much as the math.

Solo practice cannot reproduce the pressure of a live multiplayer round, but it can prepare the basics: fast expected-value recalculation, how spread width should scale with uncertainty and inventory, and the economics of market making.

Behavioral and fit interviews

"Why trading?" and "Why this firm?" come up in nearly every process. Interviewers use them to check that you understand the day-to-day job: long stretches without clear feedback, real money lost on well-reasoned decisions, and competitive, sometimes repetitive work that "the intellectual challenge" does not fully describe.

Prepare specific stories: a decision made with incomplete information, a mistake you owned and what changed afterward, a calculated risk that did not pay off, and times you took feedback well or handled disagreement. Keep each one short: situation, action, outcome, and what it shows about how you think.

Fit is assessed throughout, including in technical rounds, where interviewers note composure, coachability, and how you take a hint or pushback on a brain teaser. Getting defensive when corrected, or visibly rattled after a wrong probability answer, is remembered as much as the math.

Firm-by-firm notes

Processes change often and firms rarely publish exact formats. These notes come from public candidate reports; check the firm's current careers page and recent reports before an interview.

Optiver is the firm most associated with a branded mental math speed test, and its later rounds are widely reported to focus on options and market-making intuition. Jane Street is known for deep probability and expected-value puzzles, trading games and, for some roles, coding rounds. Flow Traders is reported to screen with a timed multiple-choice arithmetic test. IMC's trader OA is widely described as a games battery with no mental-math questions, and CTC's as 50 mixed-reasoning questions (numerical, spatial, verbal and logic) in 15 minutes. SIG is commonly reported to combine probability testing with a structured behavioral or psychometric component. Akuna and Maven Securities, among others, are reported to use third-party numerical or gamified assessments early in the funnel. Citadel Securities (the market maker) and Citadel's quantitative investing business are separate operations under the same parent group. Both, like other large multi-strategy and quant funds, tend to weight coding and applied statistics above mental-arithmetic speed, especially for research roles.

All of these firms test fast, accurate quantitative reasoning under pressure, with different weightings.

Mixed OA practice: CTC / Chicago Trading Company OA-style simulator (50 questions · 15 minutes · four reasoning families).

Common mistakes

Training speed before accuracy is stable. Rushing from day one builds habits that break down under time pressure and negative marking. Fix the error rate first, then cut the time.

Memorizing brain teasers. Interviewers change the numbers and add twists to catch memorized answers. Practice the method instead.

Never practicing under time pressure. Untimed practice at home does not prepare you for an 8-minute countdown with a proctor watching. Well before test day, practice under test conditions: the same time limit, no calculator, no pausing.

Skipping behavioral prep for a "math firm". Fit and composure are graded inside technical rounds too. Solving every brain teaser but seeming rattled or evasive on "why trading" is a common reason for rejection after a superday.

Preparing only for one firm's known format. Most firms test the same core skills, and firms do switch assessment providers. Prepare the core skills first.

A 5-week study plan