Question

Natasha and Allison are playing a tennis match where the winner must win 2 sets in order to win the match. Natasha starts strong but tires quickly. The probability that Natasha wins the first set is 0.6. However, the probability she wins the second set is only 0.55. And if a third set is needed, the probability that Natasha wins the third set is only 0.4. Put all this information into a tree diagram to answer the following questions. (a) What is the probability that Natasha wins the match? (b) If Allison wins the first set, what is the conditional probability that Natasha, instead, ends up winning the match? (c) If Natasha wins the first set, what is the conditional probability that Allison, instead, ends up winning the match? (d) What is the probability that 3 sets will be played?

Answer 1

a) probability that Natasha wins the match=P(wins first and second)+P(wins fist and lose second and wins third)+P(lose first ; wins second and wins third)=0.6*0.55+0.6*0.45*0.4+0.4*0.55*0.4=0.526

b)

P(Nataha wins|Alice wins first set)=Natasha wins next 2 set=0.55*0.4=0.22

c)

P(Alcie wins|Natasha wins first set)=Allice wins next 2 sets =0.45*0.6=0.27

d)

probability that 3 sets will be played =P(Natahsa wins fist and lose second )+P(Natasha lose first ; wins second)=0.6*0.45+0.4*0.55=0.49