Tree Diagrams Practice Questions

Question 1

4 marks

Do not use a calculator for this question.

Rosa plays two games of chess.

The probability that she wins the first game is 0.30.3

If she wins the first game, the probability that she wins the second game is 0.450.45

If she does not win the first game, the probability that she wins the second game is 0.20.2

(a)

Complete the probability tree diagram.

First gameSecond game0.3.........0.45.........0.2.........WinsDoes not winWinsDoes not winWinsDoes not win

(b)

Work out the probability that Rosa wins both games.

Question 2

2 marks

Do not use a calculator for this question.

A bag contains 55 red counters and 33 blue counters.

Kim takes at random a counter from the bag. She does not put the counter back in the bag.

She then takes at random a second counter from the bag.

Kim draws this probability tree diagram.

First counterSecond counter5/83/85/83/85/73/7RedBlueRedBlueRedBlue

The diagram is not correct.

Write down two things that are wrong with the probabilities in the probability tree diagram.