Easy · Probability & Combinatorics · Free response · ~5 min · #96

One Third from a Fair Coin

Real interview · Goldman Sachs

Using only a fair coin, describe a procedure that produces an event with probability exactly $\tfrac13$ , and give the expected number of flips it uses.

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Worked solution

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

Reported in interviews

Goldman SachsGlassdoor 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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