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A coin is tossed until a head appears, or the tail appears 4 times in succession, then the probability distribution of the number of tosses is

Solution

✅ Correct Option: 1

Tossing stops at the first head or after four tails. So P(1)=P(H)=12P(1)=P(H)=\frac{1}{2}, P(2)=P(TH)=14P(2)=P(TH)=\frac{1}{4}, P(3)=P(TTH)=18P(3)=P(TTH)=\frac{1}{8}, and P(4)=P(TTTH)+P(TTTT)=116+116=18P(4)=P(TTTH)+P(TTTT)=\frac{1}{16}+\frac{1}{16}=\frac{1}{8}. These sum to 11.

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