Miscellaneous Exam-Style Questions.

(a) There are 24 people at a Football Club supporters' meeting in Dudley. Thirteen of them are female.

First chosen                         Second chosen

Tracey draws the tree diagram above to show how two people could be chosen from the meeting at random. What is wrong with the probabilities shown on the diagram?

(b) Aynuk and Ayli play for Dudley Casuals Football Club. The probabilities that they will score a goal in the next match are 0.2 and 0.35 respectively.

The manager thinks that the probability that both players will score a goal in the next match is 0.2 + 0.35. Is the manager correct? Give reasons for your answer.

Worked Solution

Neal is attending a Scout jamboree in Japan. He has both boots and trainers to wear. He also has the choice of wearing a cap or not.

The probability Neal wears boots is 0.4. If he wears boots, the probability that he wears a cap is 0.7.

If Neal wears trainers, the probability that he wears a cap is 0.25.

The following tree diagram shows the probabilities for Neal's clothing options at the jamboree.

(a) Find the value of A.

(b) Find the value of B.

(c) Find the value of C.

(d) Calculate the probability that Neal wears trainers and no cap.

(e) Calculate the probability that Neal wears no cap.

(f) Calculate the probability that Neal wears trainers given that he is not wearing a cap.

(g) Calculate the probability that Neal wears boots on the first two days of the jamboree.

(h) Calculate the probability that Neal wears boots on one of the first two days, and trainers on the other.

Worked Solution

Julie chooses a cake from a yellow box on a shelf. The box contains two chocolate cakes and three plain cakes. She eats the cake and chooses another one from the box. The tree diagram below represents the situation with the four possible outcomes where C stands for chocolate cake and P for plain cake.

(a) Write down the value of \(x\).

(b) Write down the value of \(y\).

(c) Find the probability that both cakes are plain.

On another shelf there are two boxes, one red and one green. The red box contains four chocolate cakes and five plain cakes and the green box contains three chocolate cakes and four plain cakes. Ben randomly chooses either the red or the green box and randomly selects a cake.

(d) Copy and complete the tree diagram below.

(e) Find the probability that he chooses a chocolate cake.

(f) Find the probability that he chooses a cake from the red box given that it is a chocolate cake.

Worked Solution

Jane and David play two games of golf. The probability that Jane wins the first game is \(\frac56\). If Jane wins the first game, the probability that she wins the second game is \(\frac67\).

If Jane loses the first game, the probability that she wins the second game is \(\frac34\)

(a) Copy and complete the following tree diagram.

(b) Find the probability that Jane wins the first game and David wins the second game.

(c) Find the probability that David wins at least one game.

(d) Given that David wins at least one game, find the probability that he wins both games.

Worked Solution