<PRE><B>Question 293293</B>
A fair coin is tossed until first tail comes up. 
Let A be the event that the number of tosses is divisible by 5, 
B be the event that the number of tosses is less than 6

Find 
P(A) = P(5) + P(10) + P(15)+ ...
= (1/32) + (1/2)^10 + (1/2)^15...
----------------------------------- 
P(B) = P(1)+P(2)+...+P(5)
= (1/2) + (1/2)^2 + ...+(1/2)^5
----------------------------------- 
P(AUB) = (1/2) + (1/2)^2 +...(1/2)^5 + (1/2)^10 + (1/2)^15 + ...
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Cheers,
Stan H.
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