GATE 2014 EC (EC3) – Question 14
An unbiased coin is tossed infinitely many times. Find the probability that the fourth head appears on toss ten.
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Correct answer: (C) 0.082
Explanation
The tenth toss must be a head, and the first nine tosses must contain exactly three heads. There are C(9,3)=84compatible sequences of length10, each of probability2⁻¹⁰. Thus probability=84/1024=0.08203125, matching **0.082,C**.