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AMC 10B 2019 #21 — Coin Flip Until Two Heads/Tails or Head+Tail

1925SpecialistCombinatoricsProbability

AMC 10B · 2019 · Problem 21

Debra flips a fair coin repeatedly, keeping track of how many heads and how many tails she has seen in total, until she gets either two heads in a row or two tails in a row, at which point she stops flipping. What is the probability that she gets two heads in a row but she sees a second tail before she sees a second head?

Answer choices

A
\frac{1}{36}
B
\frac{1}{24}
C
\frac{1}{18}
D
\frac{1}{12}
E
\frac{1}{6}
0 students attempted0% solvedRating 1925

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