SOLUTION: In a sequence of independent rolls of a fair die, find the probability that i) The first 3 is observed on the fifth trial ii) At least 4 trials are required to obtain a 1

Question 1199988: In a sequence of independent rolls of a fair die, find the probability that
i) The first 3 is observed on the fifth trial
ii) At least 4 trials are required to obtain a 1

Answer by ikleyn(52909) (Show Source): You can put this solution on YOUR website!
.
In a sequence of independent rolls of a fair die, find the probability that
i) The first "3" is observed on the fifth trial
ii) At least 4 trials are required to obtain a "1"
~~~~~~~~~~~~~~~

In this my post, I will solve part (i), ONLY.

Event in part (i) is the intersection of two independent events E and F.


    Event E is that first 4 rolls are "not 3".

    Event F is that the 5-th draw is "3".


Therefore, the probability of event in part (i) is

    P(event in part (i) ) =  = .    ANSWER

Solved.

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