The most difficult company to get into on Wall Street: Jane Street, which earns 40 billion dollars a year. How crazy are their interview questions?

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This week, the most discussed topic on Wall Street is Jane Street.

With 3,500 employees, no banking license, no consulting fees, no investment banking business. Relying solely on trading, it generated $39.6 billion in revenue in 2025. Surpassing JPMorgan Chase. Surpassing Goldman Sachs. Surpassing any institution in Wall Street history.

Assuming a profit margin of 65-70%, the company’s per capita profit is approximately $8 million to $9 million. The highest in the world among companies with over 1,000 employees. Next door, Citadel Securities, with 1,800 people, has a per capita profit of $3.6 million; Hudson River Trading is only $6.6 million; even Nvidia, a company chased around the world for funding, has a per capita profit of only $2.9 million.

So this week, all financial professionals on Twitter are discussing the same question: How did Jane Street recruit these people?

The most difficult company to get into on Wall Street

The name Jane Street is not unfamiliar in the crypto circle.

FTX founder SBF’s first job was an internship at Jane Street. SBF’s ex-girlfriend Caroline Ellison, who later left Alameda with a trail of chaos, also came from there. SBF repeatedly mentioned in Michael Lewis’s book that the market thinking framework he learned at Jane Street almost determined all his trading instincts at FTX and Alameda later.

Many fund founders and project teams in the crypto space have some connection with Jane Street on their resumes before switching to crypto, but most of them have only “interviewed” there, not “received an offer.”

Zhu Su, founder of Three Arrows Capital, also tweeted recalling: “In December 2008, I interviewed at Jane Street in Tokyo and Hong Kong. My friend was working at their Tokyo office, a PhD in architecture from Tokyo University who switched to quant trading. After the second round, I realized one thing: I should learn programming, not just Excel.”

Monad Foundation growth lead retweeted a question he was asked in his sophomore year at MIT, saying “I still remember how crazy that interview was.” Brian, co-founder of Glider Finance, is also following the discussion about the long-standing cipher lock puzzle from Jane Street.

Many veteran players in the crypto circle have brushed shoulders with this company at some point.

And the difficulty of interviewing at Jane Street is among the top on Wall Street. According to the grading of candidate interview difficulty by Twitter user @vivoplt, Jane Street is at the top of difficulty S+, on par with top AI labs.

A tweet from Hampton about his 2012 interview. It sounds a bit like dark humor: meeting at Fulton Street in the Financial District, next to the World Trade Center, beside a Bank of America ATM. Then the interviewer took him on the A train heading toward Central Park. They played chess on the subway, but without a board, just spoken aloud. Tossing a coin to decide whether to start with 1.e4 or 1.d4. If no decision is reached by 59th Street Columbus Circle, they start a blitz game, playing all the way to Central Park. Hampton said he lost at a stop in Times Square.

Another investor, Alex Song, recalled his 2010 Jane Street interview: “The worst interview of my life. An hour, the guy across explained the rules of some card game, and I had to find the winning strategy within an hour. It’s definitely not something like the Putnam Math Competition, but it was worse than D.E. Shaw, QVT, or DRW.”

Another tweeter who retweeted added: This Alex later went on to Stanford as an undergrad, then worked in fixed income trading at Morgan Stanley, then at Bain Capital in fixed income investing, earned an MBA at Harvard, worked at top hedge funds, and was a recruiting lead at Ramp early on. But Jane Street didn’t want him.

Some interviewees say: “This remains the hardest interview process in investment banking. You can prepare for other companies, but you really can’t prepare for Jane Street.” Someone even joked: “If Oppenheimer were still alive, I’d bet he still wouldn’t pass Jane Street’s third-round interview.”

Difficult interview questions

Listening to stories is not enough. Here are some questions that have been repeatedly discussed on Twitter. The editor has selected a few of varying difficulty, and readers can try them out to see how many they can solve.

Question 1: “Estimate how many windows are in New York City? Explain your methodology.”

Question 2: “How many Marines do you think are needed to overthrow a major Middle Eastern country?”

Question 3: “A safe has a six-digit password. The lock indicates whether the first four or more digits are correct, but only opens fully if all six are correct. What is the optimal strategy to find the password with the fewest attempts?”

Question 4: “You have 30 real strings (not code strings). Tie all 60 endpoints randomly in pairs. How many rings do you expect to form? For example: tying both ends of one string = 1 ring; 30 strings all tied this way = 30 rings. Tying two strings’ ends together = 1 big ring; tying all 30 strings pairwise = 15 rings.”

Question 5: “What is the next date after today where all digits are different? Format DD/MM/YYYY. How confident are you?”

Question 6: “What integer is closest to the square root of 1420?”

Question 7: “What is the probability that a relative of mine is a professional baseball player?”

Question 8: “What is the smallest positive integer composed only of 1s and 0s that is divisible by 15?”

Question 9: “What is the angle between the hour and minute hands at 3:15 PM?”

Question 10: “You have a chance to bid on a treasure chest. Its true value is somewhere between $0 and $1000, and you are 100% confident it’s within this range. If your bid is equal to or higher than the actual value, you get the chest at your bid; if lower, you get nothing. Meanwhile, a friend is willing to buy it from you at 1.5 times its true value. How much should you bid?”

Question 11: “I roll a 20-sided die (numbers 1 to 20). How much are you willing to pay to play this game, where your payout equals the number on the die? Now change the rules: each round, you can choose to ‘take the current number’ or ‘reroll.’ You do this for 100 rounds. What is your optimal strategy? What is the value of this game?”

Question 12: “A blackboard has 100 sentences. Sentence 1 says ‘At most 0 of these 100 sentences are true.’ Sentence 2 says ‘At most 1 of these 100 sentences are true’… Sentence n says ‘At most n−1 of these 100 sentences are true.’ Sentence 100 says ‘At most 99 of these 100 sentences are true.’ How many of these sentences are actually true?”

Question 13: “I flip 4 coins. What is the expected number of heads? Now you get one chance to re-flip all 4 coins (must accept the new result). What is the expected value now?”

Question 14: “Two equally skilled teams play a best-of-seven series. What is the probability that the series goes to Game 7?”

Question 15: “Suppose you co-host a party with a roommate and invite 10 other pairs of roommates. During the party, you ask each person except yourself: ‘How many people have you shaken hands with?’ Knowing that no one shook hands with their own roommate, and everyone gives a different answer, how many times did your roommate shake hands?”

Question 16: “100 prisoners are locked in 100 separate cells. There is only one light bulb room, and only one prisoner can enter at a time, to turn the light on or off. Prisoners are called into the bulb room randomly, with no control over the order or number of visits. Any prisoner can at any time declare: ‘All 100 of us have been in this room.’ If correct, everyone is released; if wrong, everyone is executed. Before the game starts, prisoners can plan strategies, but no communication is allowed after. What is the optimal strategy?”

Question 17: “Suppose I have 10 coins. One is a fair coin (50/50 heads/tails), and the other 9 are biased, but each bias is unknown. With limited flips, how do you identify the fair coin?”

Question 18: “1000 ninjas stand in a circle, each holding a sword. Ninja 1 kills Ninja 2, Ninja 3 kills Ninja 4, Ninja 5 kills Ninja 6, and so on, continuing around the circle until only one remains. Which ninja number is it?”