Fifty Steps of Two Percent
Estimate to two decimal places, with no calculator and no paper, in under thirty seconds. Then say how confident you are in the second decimal place, and why.
Five Rings Interview Guide
Five Rings opens with a phone screen where roughly 10 to 19 questions arrive read aloud on a 15 to 30 second countdown, before probability and game theory get any slower.
Sample Five Rings questions
Three Tokens and a Bluffing Rate
Ada and Bo play a stripped-down poker game. Three tokens marked , , and are shuffled; one is dealt face down to each player and the third is set aside unseen. Each player antes , so the pot is .
Only Ada acts. She may **check**, in which case the tokens are revealed and the higher one takes the pot; or she may **bet **, after which Bo either **folds** (Ada takes the pot) or **calls **, after which the tokens are revealed and the higher one takes the pot.
Both players know the rules and each other's strategies; neither can be exploited. Find the equilibrium: how often should Ada bet with the , and how often should Bo call with the ?
The Ratio of Two Dice
You roll two fair eight-sided dice, independently, showing and (each uniform on ). Compute .
Before computing, say what your instinct is, and then say whether your instinct was right.
First-round phone screen
A brief behavioral opener, then rapid-fire math
What to expect
- A short behavioral opener on background and interest in trading.
- Then roughly 10 to 19 rapid-fire questions, read aloud with a 15 to 30 second countdown each.
- Estimation and Fermi problems mixed with mental math: square roots, fraction division, logarithms.
- The clock covers hearing the question as well as answering it, so a fast rough answer beats a slow exact one.
How to prepare
- Drill mental math against a countdown, not just untimed, since the clock is the whole point of this round.
- Practice a handful of Fermi estimates until you have a default structure for an unfamiliar one.
- Say a rough answer early and refine it, rather than staying silent while you compute exactly.
Trader interviews
Depth over speed, escalating on purpose
What to expect
- Probability, statistics, stochastic processes and game theory, in more depth than the phone screen.
- A question often starts simple, then gets modified and generalized as you answer.
- Interviewers keep pushing until you reach something you cannot immediately do.
- Stating your assumptions is weighed alongside reaching a correct answer.
How to prepare
- Practice narrating assumptions out loud before committing to a number.
- Expect a comfortable answer to be extended into a harder version; do not treat the first answer as the end of the question.
Game and strategy round
Bluffing and bidding scenarios, not brainteasers
What to expect
- A simplified poker-style game where you work out optimal bluffing probabilities with the interviewer.
- Bidding or auction scenarios that turn on expected-value optimization.
- The interviewer participates rather than just grading, so it plays out as a real back-and-forth.
How to prepare
- Review basic game-theory setups: mixed strategies, bluffing frequencies and simple auctions.
- Practice thinking a step ahead of your own first move, since the game keeps evolving as you play.
Final onsite
Several sessions with traders, quants and developers
What to expect
- Several further sessions of advanced probability and game-theory problems.
- Open-ended hypotheticals alongside the technical content.
- Cultural-fit conversations across the day, plus reference checks.
- Meetings with traders, quants and developers, not only the desk you applied to.
How to prepare
- Pace yourself for a full day of technical rounds; fatigue late in the day is a real factor here.
- Keep one or two personal stories ready for the fit conversations, since they run alongside the technical sessions.
Drill fast mental math under a clock
More reported Five Rings questions
Yeast in Overdrive
A brewery's yeast culture doubles every minutes under ideal conditions. A technician checks the tank at minutes and counts cells (in appropriate units). What count should the technician expect at minutes?
Stacking Gaussians
Let be independent random variables, each distributed as (mean , variance ). The probability can be written as , where is the standard normal CDF. Find .
Landmarks for a Log and a Power
No calculator, roughly thirty seconds each. Estimate:
(a)
(b)
State the landmark constants you are leaning on.
Every Four From One to Five Thousand
Write out every integer from to in a long list. How many times does the digit appear in total? (Note that a number like contributes three occurrences.)
Follow-up: how many of those numbers contain at least one ?
Peaks Around the Round Table
Seven judges sit at a round table, each with a distinct score written on a card in front of them. The seven cards are dealt to the seven seats uniformly at random. Call a seat a **peak** if its score is higher than the scores at both of the seats immediately beside it.
What is the expected number of peaks? Then generalise to seats.
Two Spins Against One
A carnival booth runs this game. You spin a fair six-sided spinner **twice** and keep your better result. The house spins the same spinner **once**. You win if your kept number is strictly greater than the house's; if the two are equal the game is a push and your stake is returned; otherwise you lose your stake.
(a) What is your probability of winning?
(b) At even money on a stake, what is your expected profit per play?
The First Repeated Bin Code
A warehouse scanner assigns each incoming parcel a bin code drawn uniformly at random from codes, independently each time and with repetition allowed. Let be the number of the parcel that first receives a code already used by an earlier parcel.
Estimate . Give a general formula in terms of the number of codes .
FAQ
What is the Five Rings phone screen format?
A 20 to 30 minute call: a short behavioral opener, then roughly 10 to 19 rapid-fire questions read aloud with a 15 to 30 second countdown each, mixing Fermi estimates with mental math like square roots, fraction division and logarithms. The clock includes the time it takes to hear the question, so a fast rough answer beats a slow exact one.
What happens in the Five Rings trader interviews?
One to three calls of 45 to 60 minutes going deeper into probability, statistics, stochastic processes and game theory. A question typically starts simple, then gets modified and generalized as you answer, and interviewers keep pushing until you reach something you cannot immediately solve. Stating your assumptions is scored alongside the final answer.
Does Five Rings use a game or strategy round?
Yes. Candidates solve a collaborative game live with a trader, such as a simplified poker-style bluffing problem or a bidding and auction scenario built on expected-value optimization. The interviewer plays along rather than only grading, so it runs as a genuine back-and-forth before the final onsite.