Atournament is being run between two teams, a and b. this is a 2- tournament meaning that the first team to win 2 games is the tournament winner (sometimes called a best-two-out-of-three tournament). for the first game, the probability of a winning is pa wins]-1/3. for all ensuing games the probability that team a wins is pa wins- 1/3 unless team a lost on the previous round in which case pa wins-3/5.

a: what is the probability that the tournament requires the full three games to decide a winner?
b: the tournament concludes after two games. what is the probability that a won?

Step-by-step explanation:

For first game PA = 1/3

For second game PA = 1/3 ( If A is not lost in first game )

 = 2/5 (If A is lost in first game )

For conclusion of game in three matches :

If A wins , the probability is

PA , PB , PA  = 1/3 X 2/3 X 3/5 = 6/45

PB , PA , PA = 2/3 X 3/5 X 1/3 = 6/45

If B wins

PA, PB, PB = 1/3 X 2/3 X 2/5 =  4/ 45

PB, PA , PB = 2/3 X 3/5 X 2/3 = 4 / 15

Total probability of conclusion of game in 3 matches

= 6/45 +6/45 + 4/45 +4/15 = 28/45

b )

For the game concluding in 2 matches , the probability are as follows

PA,PA = 1/3 X 1/3 = 1/9

PBPB = 2/3 X 2/5 = 4 / 15

Total probability

= 1/9 + 4/15 = 17/45

So PA = 1/9 / 17/45

= 5/17