Easy · Probability & Combinatorics · Free response · ~6 min · #74

Simulate a Die with a Coin

Real interview · J.P. Morgan, Jane Street

A board game needs a die, but you only have a fair coin. Describe how to generate each of the numbers 1–6 with probability exactly $\tfrac16$ , and give the expected number of flips your method uses.

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Worked solution

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

Reported in interviews

J.P. MorganGlassdoor interview question
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

Rejection samplingGeometric distribution

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