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2019 AMC 10B Problem 21

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2019 AMC 10B Problem 21AMC 10 Step by Step
Name:                             Date: September 13, 2026
Conditional Probability & States · difficulty 4 of 5 · about 6 min · position P21-25

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?

  1. A)

    136\frac{1}{36}

  2. B)

    124\frac{1}{24}

  3. C)

    118\frac{1}{18}

  4. D)

    112\frac{1}{12}

  5. E)

    16\frac{1}{6}

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