Jane Street

www.janestreet.com
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## 1 Candidate Interview Review Back to all Interviews

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## Assista Interview

No Offer
Neutral Experience
Difficult Interview

Application

The process took 2 weeksinterviewed at Jane Street (London, England (UK)) in May 2012.

Interview

Submitted application, got email back for phone interview about a week later. First round interview went straight into mental maths, then some probability questions. Second round was harder probability questions.

Both interviews were late, and the second round had to be rescheduled due to the interviewer forgetting. Both interviewers were very friendly though!

Interview Questions

• 1st Round: You toss 4 coins in the air, and win the number of heads shown. If you choose, you may reflip all 4 coins and must take the second result. What is the value of this game?   1 Answer
• 1st Round: You're playing a game where you and an opponent have fair coins. You flip your coin first, and if you get H you win £10. If you get T your opponent may flip, and if he gets H he wins £10.

The game continues in this manner until a H is tossed. What is your expected value?

• 1st Round: You can buy an item in boxes of 3, 8 or 20. What's the highest integer that it's unable to obtain by buying in combinations of these boxes?   5 Answers
• 2nd Round: You have a six-sided die and a ten-sided die. You are offered a game where you can guess at the sum of these two dice, and if you are correct you win the number on the dice.

What's the optimal strategy, and what's your expected value?

• 2nd Round: You have a deck of cards, 26 red, 26 black. These are turned over, and at any point you may stop and exclaim "The next card is red.". If the next card is red you win £10.

What's the optimal strategy? Prove this is the optimal strategy.

## Jane Street

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