A fair coin is tossed 4 times. What is the probability that two heads do <strong>NOT</strong> occur consecutively?

  1. A. 1/8
  2. B. 3/8
  3. C. 7/16
  4. D. 1/2

Correct Answer: D. 1/2

Explanation

Let n=4 be the number of coin tosses. The total number of possible outcomes is 2^4 = 16. The valid sequences without consecutive heads are TTTT, TTTH, TTHT, THTT, HTTT, THTH, HTHT, and HTTH, which total 8 outcomes (following the Fibonacci sequence F_{n+2} = F_6 = 8). The probability is \frac{8}{16} = \frac{1}{2}.

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