Medium · Brain Teasers & Logic · Multiple choice · ~5 min · #57

Guess 100 Flips with One Question

Real interview · Jane Street

I flip a fair coin 100 times and write down the sequence. You may ask one yes/no question, then you must guess the whole sequence.

What is the highest probability of guessing correctly that any question can achieve?

Hints · 0 of 2 shown

Worked solution

Give the problem an honest attempt first, then reveal the full explanation.

Reported in interviews

Jane StreetGlassdoor interview question

Candidate-reported and unverified; the firm may phrase it differently or no longer ask it. The wording here is our own paraphrase, and the solution was written and checked independently of any answers posted at the source.

Concepts

Partitioning outcomesInformation

Relevant for

Quant TraderQuant ResearcherQuant Developer