481.Race to Three of a Kind
★★★expected valueCh. 6 — Random Variables and Expectation444+ Problems in Probability
Anna and Brenda repeatedly toss a fair coin. Anna wins once 3 heads have appeared in total; Brenda wins once 3 tails have appeared in total (not necessarily consecutive). What is the expected number of tosses until someone wins?
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The game ends on toss 3, 4, or 5. Enumerate how many of the 32 length-5 sequences end at each length.
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