Prep by Firm

Citadel Securities interview prep: train the exact formats

One of the most selective funnels in trading: a timed quantitative screen, then rounds that hammer expected value, conditional probability and market-making scenarios, with mental arithmetic speed assumed throughout. Every one of those formats has a matching drill here, free, in your browser.

Open the Citadel Securities training plan Try the probability bank first

What the Citadel Securities process tests

A timed online assessment mixing mental math, probability and quantitative reasoning, no calculator; the exact format varies by role and year.
Expected value and conditional probability: interview rounds built on EV, Bayes and updating on new information.
Multi-stage games and random walks: rerolls, betting sequences, gambler's-ruin flavors.
Market-making scenarios: quote a two-sided market, get filled, manage the risk, defend the price.
Brainteasers and data interpretation threaded through the live rounds.

Warm up on the real thing

Screen pace, no calculator: what is 17% of 340?

57.8. 10% is 34, 7% is 23.8, sum them. Splitting percentages into 10-5-1 blocks is the reflex their timed screen rewards.

A coin is either fair or double-headed, equal prior. You flip it three times: heads, heads, heads. Probability it is the double-headed one?

8/9. Likelihood ratio: the double-header produces HHH with probability 1, the fair coin with 1/8. Posterior odds 8:1, so 8/9. Bayesian updating on a likelihood ratio is the single most recycled interview move here.

Roll a die. You may keep the face value or reroll once, but then you must keep the second roll. Fair value of the game?

4.25. A reroll is worth 3.5 on average, so keep any first roll above 3.5: keep 4, 5, 6, reroll 1, 2, 3. Value = (4+5+6)/6 + (3/6)(3.5) = 2.5 + 1.75. Multi-stage games like this are their bread and butter; always price the continuation first.

A ready-made training plan

The app's Prep by Firm desk has a Citadel Securities card that maps each stage of their process onto the right drill and launches it in one click: an 80-in-8 arithmetic sprint to overtrain the no-calculator speed, the Odds Sprint (15 fast probability calls on a per-question clock), a probability study set on expected value, Bayes, random walks, game theory and market intuition, the brainteaser desk with an AI examiner, the market-making arena, and a full timed interview simulation. Your best scores are tracked per format so you can see where the bar still is.

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Explore the rest of the desk

Mental MathZen, timed and sprint drills across 11 categories Probability Lab285 interview questions with worked solutions BrainteasersClassic puzzles with progressive hints and AI grading Market Maker ArenaQuote two-sided markets against informed flow Interview SimA timed, three-part mock with a debrief

Based on public interview reports and candidate accounts; formats change, so verify the current process with your recruiter. My Quant Journey is independent: not affiliated with, sponsored by or endorsed by Citadel Securities.