<PRE><B>Question 574385</B>
Define the following two events for two tosses of a coin: 
A = at least one head is obtained 
B = both tails are obtained 
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P(2 tails) = (1/2)^2 = 1/4
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P( at least one head) = 1 - P(no heads) = 1 - (1/4) = 3/4
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Cheers,
Stan H.  </PRE>