Prep by Firm

Five Rings interview prep: train the exact formats

Often described as a Jane Street funnel turned up a notch: a screen of rapid estimation answered as bounds you would defend, then a long virtual day of probability, game theory and stochastic reasoning with traders and quants. Every one of those formats has a matching drill here, free, in your browser.

Open the Five Rings training plan Try estimation first

What the Five Rings process tests

A rapid estimation screen: reports mention about 18 questions at 20 to 30 seconds each, answered as a lower and upper bound.
Probability and expected-value puzzles, usually multi-step.
Game theory: betting games, auctions, adversarial reasoning.
Stochastic flavors in later rounds: random walks, Markov chains, stopping intuition.
A full virtual Super Day of back-to-back 1:1 and 2:1 technical interviews.

Warm up on the real thing

Screen pace, 25 seconds: how many commercial flights take off worldwide per day? Give bounds you would bet on.

Order 10⁵: say 60,000 to 150,000. Roughly 25,000 airliners in service, each flying 3 to 5 legs a day. The interviewer grades the width and honesty of your interval as much as the midpoint; a bound you cannot defend is worse than a wide one.

You have $1, your opponent has $2. You bet $1 on a fair coin flip repeatedly until one of you is broke. Probability you end up with all $3?

1/3. In a fair game the ruin probability is proportional to your share of the total capital: 1 out of 3. Gambler's-ruin identities like this are the "stochastic flavor" their later rounds reach for.

Two dice are rolled. Given that the sum is 8, what is the probability at least one die shows a 6?

2/5. The sum-8 outcomes are (2,6), (3,5), (4,4), (5,3), (6,2): five equally likely cases, two contain a six. Conditioning by enumerating the reduced sample space is the clean fast route; most wrong answers come from forgetting (4,4) has no twin.

A ready-made training plan

The app's Prep by Firm desk has a Five Rings card that maps each stage of their process onto the right drill and launches it in one click: the Fermi Lab for estimation trained on log-distance (being roughly right, fast), the Odds Sprint at their 20-to-30-second screening pace, a probability study set on classics, expected value, random walks and game theory at the hard end, the brainteaser desk with an AI examiner that pushes back, the market-making arena for adversarial pricing, and a full timed interview simulation to build stamina for the long day. Your best scores are tracked per format so you can see where the bar still is.

Start the Five Rings plan free

Prep for other firms

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Explore the rest of the desk

Fermi LabEstimation problems scored on log-distance 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 Five Rings.