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10.02 Introduction to multi-stage experiments

Worksheet
Independent events
1

Write an equation for P \left( A \text{ and } B \right) in terms of P \left( A \right) and P \left( B \right) given that the two events are independent.

2

A password must five characters long, consisting of only lowercase letters and numbers. How many different passwords are possible?

3

A coin is tossed, a die is rolled, and a card is randomly selected from a normal deck of cards.

a

Find the total number of outcomes.

b

Find the probability that the coin lands on heads, the die lands on 6 and an Ace of Hearts is selected from the deck of cards.

c

Find the probability that the coin lands on tails, the die lands on an even number, and the card selected is red.

4

Three ordinary dice are rolled. Find the probability that all three dice show a number less than 3.

5

Robert has found that when playing chess against the computer, he wins \dfrac{1}{2} of the time.

a

Find the probability that he wins:

i

Two games in a row.

ii

Three games in a row.

iii

At least one of two games.

iv

At least one of three games.

b

Which of these events does Robert have a better chance of winning?

6

On a roulette table, a ball can land on one of 18 red or 18 black numbers.

a

If it lands on a red number on the first go, find the probability that it will land on a red number on the second go.

b

Are the successive events of twice landing on a red number dependent or independent?

c

In a game of roulette, the ball has landed on a black number 6 times in a row. Which of the following statements are true:

A

It is highly likely that the ball will land on black the next go.

B

It is highly unlikely that the ball will land on black again the next go.

C

The ball is equally likely to land on a black or red in the next go.

Lists
7

Luke can’t remember the order of his pin for his EFTPOS card, but he knows it contains the digits in 2853. Listed below are all the possible combinations of Luke’s pin beginning with 2 and 8:

2853, 2385, 8523, 2835, 2358, 8532, 2583, 8253, 8325, 2538, 8235, 8352
a

List all the other possible combinations of pins.

b

State the total number of possible outcomes.

c

Find the probability his pin starts with 5.

d

Find the probability his pin has 5 followed immediately by 2.

e

Find the probability his pin starts with 8, or ends with 3, or both.

8

Buzz can’t remember the combination for his lock, but he knows it is a three digit number and contains the digits 6, 8 and 9.

a

List all possible locker combinations that Buzz should try.

b

State the total number of possible outcomes.

c

If Buzz is correct that the combination includes 6, 8 and 9, find the probability that:

i

The combination starts with 6.

ii

The combination starts with 6 and ends with 8.

iii

The combination starts with 6 or ends with 9.

9

A three-digit number is to be formed from the digits 4, 5 and 9, where the digits cannot be repeated.

a

List all the possible numbers in the sample space.

b

Find the probability that the number formed is:

i

Odd

ii

Even

iii

Less than 900.

iv

Divisible by 5.

Tables
10

Two standard six-sided dice are rolled at the same time.

a

Write out all the possible outcomes in a table.

b

Find the probability of tossing two heads.

c

Find the probability of tossing at least one head.

11

A standard six-sided die is rolled and a coin is tossed at the same time.

a

Write out all the possible outcomes in a table.

b

Find the probability of tossing a heads and rolling an even number.

c

Find the probability of tossing a heads or rolling an even number.

d

Find the probability of tossing a tails and rolling a number greater than 2.

12

The following two spinners are spun and the result of each spin is recorded:

a

Complete the given table to represent all possible combinations:

b

State the total number of possible outcomes.

c

Find the probability that the spinner lands on a consonant and an even number.

SpinnerABC
11,A⬚,⬚⬚,⬚
2⬚,⬚⬚,⬚2,C
3⬚,⬚⬚,⬚⬚,⬚
d

Find the probability that the spinner lands on a vowel or a prime number.

13

The following spinner is spun and a normal six-sided die is rolled. The result of each is recorded:

WXYZ
11,W⬚,⬚⬚,⬚⬚,⬚
2⬚,⬚⬚,⬚⬚,⬚2,Z
3⬚,⬚⬚,⬚⬚,⬚⬚,⬚
4⬚,⬚⬚,⬚⬚,⬚⬚,⬚
5⬚,⬚5,X⬚,⬚⬚,⬚
6⬚,⬚⬚,⬚⬚,⬚⬚,⬚
a

Complete the table above to represent all possible combinations.

b

State the total number of possible outcomes.

c

Find the probability that the spinner lands on X and the dice rolls a prime number.

d

Find the probability that the spinner lands on W and the dice rolls a factor of 6.

e

Find the probability that the spinner doesn’t land on Z or the dice doesn't roll a multiple of 3.

Tree diagrams
14

Three cards labeled 1, 2, 3 are placed face down on a table. Two of the cards are selected randomly to form a two-digit number. The possible outcomes are displayed in the following probability tree:

a

List the sample space of two digit numbers produced by this process.

b

Find the probability that 2 is a digit in the number.

c

Find the probability that the sum of the two selected cards is even.

d

Find the probability of forming a number greater than 40.

15

A coin is tossed twice.

a

Construct a tree diagram to identify the sample space of tossing a coin twice.

b

Use the tree diagram to find the probability of getting two tails.

c

Use the tree diagram to find the probability of getting at least one tail.

16

Ivan rolled a standard die and then tossed a coin.

a

Construct a tree diagram to identify the sample space of rolling a standard die and then tossing a coin.

b

List all the possible outcomes in the sample space.

c

Find the probability of the result including an odd number.

d

Find the probability that the result includes a number less than or equal to 5, and a tail.

17

Han has a special three-sided die with the numbers 1, 2 and 3 on its sides. He rolls it and then tosses a coin.

a

Construct a tree diagram to list all possible outcomes.

b

Using the tree diagram, find the probability of a 1 and a tail.

c

Using the tree diagram, find the probability of an outcome with a head.

d

Using the tree diagram, find the probability of an outcome with an odd number.

18

Construct a tree diagram showing the following:

a

All possible outcomes of boys and girls that a couple with three children can possibly have.

b

All the ways the names of three candidates; Alvin, Sally and Peter, can be listed on a ballot paper.

19

Every morning Mae has toast for breakfast. Each day she either chooses honey or jam to spread on her toast, with equal chance of choosing either one.

a

Construct a tree diagram for three consecutive days of Mae’s breakfast choices.

b

Find the probability that on the fourth day Mae chooses honey for her toast.

c

Find the probability that Mae chooses jam for her toast three days in a row.

20

A die is rolled twice.

a

Construct a tree diagram showing all the possible results of the given experiment.

b

Use the tree diagram to find the probability of rolling:

i

A double 5.

ii

The same number twice.

iii

Two different numbers.

iv

Two odd numbers.

21

On the island of Timbuktoo the probability that a set of traffic lights shows red, yellow or green is equally likely. Christa is travelling down a road where there are two sets of traffic lights.

a

Construct a tree diagram to indicate the possible pairs of traffic lights.

b

Find the probability that both sets of traffic lights will be yellow.

22

Three fair coins are tossed.

a

Construct the tree diagram for the experiment given.

b

Find the probability of obtaining:

i

At least one head.

ii

TTH in this order.

iii

THH in this order.

23

A bag contains four marbles - red, green, blue and yellow. Beth randomly selects a marble, returns the marble to the bag and selects another marble.

a

Construct a tree diagram for the experiment given.

b

Find the probability of Beth selecting:

i

A blue and a yellow marble.

ii

A blue followed by a yellow marble.

iii

2 red marbles.

iv

2 marbles of the same colour.

v

2 marbles of different colours.

Probability trees
24

James owns four green jackets and three blue jackets. He selects one of the jackets at random for himself and then another jacket at random for his friend.

a

Construct a probability tree of this situation with the correct probability on each branch.

b

Find the probability that James selects a blue jacket for himself.

c

Find the probability that both jackets James selects are green.

25

An archer has three arrows that each have a probability of \dfrac{1}{5} of striking a target. If all three arrows are shot at a target:

a

Construct a probability tree showing all the possible outcomes and probabilities.

b

Find the probability that all three arrows will hit the target.

c

Find the probability that at least one arrow will miss the target.

d

Find the probability that at least one arrow will hit the target.

26

Luke plays three tennis matches. In each match he has 60\% chance of winning.

a

Construct a probability tree showing all his possible outcomes and probabilities in these three matches.

b

Find the probability that he will win all his matches.

c

Find the probability that he will lose all his matches.

d

Find the probability that he will win more matches than he loses.

27

A fair coin is tossed and then the following spinner is spun:

a

Construct a probability tree representing the situation.

b

Find the probability of getting a tail and then a yellow.

c

Find the probability of getting a tail, a yellow, or both.

d

Find the probability of getting a head and not getting a red.

e

Find the probability of not getting a head or a red.

28

A bucket contains 5 green buttons and 7 black buttons. Two buttons are selected in succession from the bucket. The first button is replaced before the second button is selected.

a

Construct a tree diagram of this situation with the correct probability on each branch.

b

Find the probability of selecting two black buttons

29

One cube has 4 red faces and 2 blue faces, another cube has 3 red faces and 3 blue faces, and the final cube has 2 red faces and 4 blue faces. The three cubes are rolled like dice.

a

Construct a probability tree diagram that shows all possible outcomes and probabilities.

b

Find the probability that three red faces are rolled.

c

Find the probability that more red faces than blue faces are rolled.

d

Find the probability that only one cube rolls a blue face.

30

The proportion of scholarship recipients at a particular university is \dfrac{7}{10}. The number of students at the university is so large that even if a student is removed, we can say that the proportion of scholarship recipients remains the same. If three students are selected at random:

a

Construct a probability tree showing all the possible combinations of recipients and nonrecipients.

b

Find the probability that at least one of the students is a scholarship recipient.

c

Find the probability that at least one of the students is a nonrecipient.

d

Find the probability there is at least one recipient and one nonrecipient in the selection.

31

A coin is tossed, then the spinner shown is spun and either lands on A, B or C.

Segment B is \dfrac{1}{8} of the entire cirle.

a

Construct a probability tree diagram showing all possible outcomes and probabilities.

b

Find the probability of landing on tails and the spinner landing on A.

c

Find the probability of landing on tails, or the spinner landing on A, or both.

32

For breakfast, Maria has something to eat and drinks a hot drink. She will either eat toast or cereal and will drink tea or Milo.

  • The chance of Maria making toast is 0.7.

  • The chance of Maria drinking Milo is 0.4.

a

Construct a tree diagram illustrating all possible combinations of food and drink Maria can have for breakfast and their associated probabilities.

b

Find the probability Maria drinks tea and eats toast.

c

Find the probability Maria drinks tea or eats toast.

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Outcomes

MA11-7

uses concepts and techniques from probability to present and interpret data and solve problems in a variety of contexts, including the use of probability distributions

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