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17.03 Probability as a number

Worksheet
Probability of an event
1

State the likelihood that corresponds to each of the following probabilities out of the following: Impossible, Unlikely, Likely or Certain.

a

0.1

b

1

c

0

d

0.6

e

\dfrac{9}{10}

f

\dfrac{2}{10}

g

\dfrac{4}{5}

h

\dfrac{1}{8}

i

10\%

j

70\%

2

Estimate the probability of the following events:

a

It will rain somewhere in Australia sometime this month.

b

You meet someone today and correctly guess their birthday.

3

Find the probability of the following events:

a

You roll a six-sided die and get 5 or more.

b

You roll a twelve-sided die and get 3 or more.

c

An event that will never occur.

d

An event that will occur 2 times every 50 trials.

e

An event that will occur 2 times every 100 trials.

f

An event that will occur 2 times every 500 trials.

4

A twelve-sided die is rolled.

a

Find the probability of rolling 5 or more.

b

Find the probability of rolling less than 5.

c

Find the probability of rolling 3 or more.

5

For each of the following spinners, find the probability of getting a star. Write your answer as a percentage.

a
b
c
d
6

A jar contains 10 marbles in total. Some of the marbles are blue and the rest are red.

a

If the probability of picking a red marble is \dfrac{4}{10}, how many red marbles are there in the jar?

b

Find the probability of picking a blue marble.

7

Paul has 23 marbles in a bag and 4 of them are black. Paul picks a marble from the bag without looking. Find the probability that Paul picks a black marble.

Events with multiple possibilities
8

Consider this list of numbers: 2,\, 2,\, 2,\, 3,\, 3,\, 3,\, 4,\, 4,\, 5,\, 5,\, 5,\, 7,\, 7,\, 7,\, 7,\, 9,\, 9

a

How many numbers are in the list?

b

A number is chosen from the list at random. Find the probability that it is an odd number.

c

State the number that has the same probability of being picked as 4.

d

A number is chosen from the list at random. State the number that has the highest probability of being chosen.

9

Consider the following spinner:

Find the probability of spinning:

a

A pig.

b

A ball or a pig.

c

A pig or an apple.

d

An apple or a star.

10

Consider the following spinner:

a

Find the probability of getting the following shapes. Simplify your answers.

i

An apple.

ii

A pig.

iii

An elephant.

iv

A ball.

v

A pig or a ball.

vi

Anything but an apple.

vii

An elephant, a star or a teddy bear.

viii

Anything but a ball or teddy bear.

b

Determine whether the following events have a probability less than 10\%.

i

Spinning a teddy bear.

ii

Spinning a star.

iii

Spinning an apple.

iv

Spinning a ball or an elephant.

11

A single marble is drawn from the following jar 5 red, 7 blue and 8 black marbles:

a

Find the probability of drawing a blue marble. Give your answer as a percentage.

b

Find the probability of drawing a blue marble or a red marble. Give your answer as a percentage.

12

A standard deck of 52 cards is shown below:

a

If a card is selected at random, find the probability that it is:

i

A red card.

ii

A red card or a King.

iii

A card between 5 and 9 inclusive.

iv

A red card that has a number between 5 and 9 inclusive.

v

A red card that has a number more than 2 and at most 9.

vi

A black or Kings, but not both.

vii

A spade, with a number printed on it.

viii

The Jack of Hearts or the Jack of Clubs.

b

Rosey draws a 6 of Spades and puts it back in the deck and asks you to draw a card. Find the probability that you will draw a card with a number larger than 6, and the same colour as Rosey's card.

Complementary events
13

The probability of the local football team winning their grand final is 0.36. Find the probability that they won't win the grand final.

14

The probability that it hails today is 0.43. Find the probability that it doesn't hail.

15

The probability that Victoria will win the major prize in a raffle at the school fete is 0.053. Find the probability that Victoria will not win.

16

A company that makes sprockets guarantees that they will be within 0.5\text{ mm} either way of the client's chosen size. There is a probability of 0.968 that a sprocket will be within the allowable size. Find the probability that a sprocket won't be within the allowable size.

17

A number between 1 and 20 inclusive is randomly picked. Find:

a

The probability that the number is at least 8.

b

The probability that the number is less than 8.

18

A number between 1 and 50 inclusive is randomly picked. The probability that the number is less than 42 is \dfrac{82}{100}.

a

State the complement of drawing a number less than 42.

b

Find the probability of this complement.

c

State the complement of drawing a number that is at least 43.

19

A letter is chosen at random from the word ORDERED.

a

State the letter that has the highest probability of not being chosen.

b

Find the probability that the chosen letter is not "D".

20

The 26 letters of the alphabet are written on pieces of paper and placed in a bag. If one letter is picked out of the bag at random, find the probability of:

a

Not selecting a B.

b

Not selecting a C.

c

Not selecting a K, R or T.

d

Not selecting a K, L or M.

e

Not selecting a A, E, I, O or U.

f

Not selecting a T, L, Q, A, K or Z.

g

Selecting a letter that is not in the word WORKBOOK.

h

Selecting a letter that is not in the word PROBABILITY.

21

A standard 6-sided die is rolled once.

a

Find the probability of rolling a prime number.

b

Find the probability of rolling an odd number.

c

Are the two events in parts (a) and (b) mutually exclusive?

d

Are the two events in parts (a) and (b) complementary?

e

Find the probability of:

i

Not rolling a 2.

ii

Not rolling a 9.

iii

Not rolling a 2 or 5.

iv

Not rolling a 1, 2, 3, 4, 5 or 6.

v

Not rolling an odd number.

22

Mario has a bag of marbles. It contains 3 white marbles and 5 marbles of other colours. Mario picks a marble from the bag without looking.

a

Find the probability that Mario picks a white marble.

b

Find the probability that Mario picks a marble that is not white.

c

Are the two events in parts (a) and (b) mutually exclusive?

d

Are the two events in parts (a) and (b) complementary?

23

A spinner has 4 sectors with a star, 4 sectors with apple, and 2 sectors with an elephant. All of the sectors are the same size.

a

Find the probability of spinning an elephant.

b

Find the probability of spinning a apple.

c

Are the two events in parts (a) and (b) mutually exclusive?

d

Are the two events in parts (a) and (b) complementary?

24
a

A bag contains red marbles and blue marbles. Given the probability of drawing a red marble is \dfrac{21}{44}, find the probability of drawing a blue marble.

b

Another bag contains 34 red marbles and 35 blue marbles. If a marble is picked at random, find:

i

P(\text{red})

ii

P(\text{not red})

25

A marble is chosen at random from a box containing 4 different colour marbles, red, blue, green and purple. The probability of selecting different colours is given in the table.

Find the probability of:

a

Not selecting a green marble.

b

Not selecting a blue marble.

c

Not selecting a purple marble.

d

Selecting a red or purple marble.

e

Selecting neither a blue or green marble.

ColourProbability
\text{Red}\quad \enspace \, \dfrac{3}{13}
\text{Blue}\quad \enspace \enspace \dfrac{2}{9}
\text{Green}\quad \enspace \enspace \dfrac{1}{5}
26

A constellation is randomly selected from the eight shown below:

a

Find the probability that the name of the constellation begins with a vowel.

b

The complementary event is selecting a constellation that begins with a consonant. Find the probability of this event.

c

Find the probability that the constellation has 6 or more stars.

d

The complementary event is selecting a constellation that has less than 6 stars. Find the probability of this event.

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MA4-21SP

represents probabilities of simple and compound events

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