<PRE><B>Question 779221</B>
A fair coin is thrown repeatedly. What is the probability that on the n th throw 
A) a head appears for the first time:: (1/2)^n
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B) the number of tails and heads to date are equal::: (n/2)(1/2)^n
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C) exactly two heads have appeared altogether to date:: nC2(1/2)^n
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D) at least two heads have appeared to date:: 1- nC(n-2)[(1/2)^n]
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Cheers,
Stan H.
</PRE>