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In a certain contest, the players are of equal skill and
Chapter 3, Problem 80P(choose chapter or problem)
Problem 80P
In a certain contest, the players are of equal skill and the probability is that a specified one of the two contestants will be the victor. In a group of 2n players, the players are paired off against each other at random. The 2n−1 winners are again paired off randomly, and so on, until a single winner remains. Consider two specified contestants, A and B, and define the events Ai, i ≤ n, E by
Ai: A plays in exactly i contests
E : A and B never play each other
(a) Find P(Ai), i = 1, ..., n.
(b) Find P(E).
(c) Let Pn = P(E). Show that
and use this formula to check the answer you obtained in part (b).
For another approach to solving this problem, note that there are a total of 2n 1 games played.
(d) Explain why 2n − 1 games are played.
Number these games, and let Bi denote the event that A and B play each other in game i,i = 1, .... 2n − 1.
(e) What is P(Bi)?
(f) Use part (e) to find P(E).
Questions & Answers
QUESTION:
Problem 80P
In a certain contest, the players are of equal skill and the probability is that a specified one of the two contestants will be the victor. In a group of 2n players, the players are paired off against each other at random. The 2n−1 winners are again paired off randomly, and so on, until a single winner remains. Consider two specified contestants, A and B, and define the events Ai, i ≤ n, E by
Ai: A plays in exactly i contests
E : A and B never play each other
(a) Find P(Ai), i = 1, ..., n.
(b) Find P(E).
(c) Let Pn = P(E). Show that
and use this formula to check the answer you obtained in part (b).
For another approach to solving this problem, note that there are a total of 2n 1 games played.
(d) Explain why 2n − 1 games are played.
Number these games, and let Bi denote the event that A and B play each other in game i,i = 1, .... 2n − 1.
(e) What is P(Bi)?
(f) Use part (e) to find P(E).
ANSWER:
Solution
Step 1 of 6
Given that :A plays in exactly i contests
Ans E:A and B never play each other
a) We have to
Her each round have the competition with probability 1/2
Any contestant go out of the 1st round is 1/2
2nd round is 1/4
3rd round is 1/8
And for i th round is (1/2)i
Hence