Rolls to a six before a five
You roll a fair die repeatedly until a appears. Given that the first occurs before the first , what is the expected number of rolls?
Show hints (2)+
- Track the wait until the first -or-: it's Geometric, mean .
- Which face (5 or 6) comes first is independent of when - so conditioning doesn't change the expected count.
Answer
Reveal answer →Final answer
3
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Asked at: Jane Street, Akuna Capital