Probability 1
This chapter is about predicting the
chance of things happening.
Jelly beans come in 60 different
flavours! If there are 65 beans
in a bag, what is the chance
of picking your favourite?
Objectives
This chapter will show you how to
• write a list of outcomes G F
• describe probability using numbers and words G F
• work out the probability of an event happening F
• work out the probability of an event not happening E
• identify mutually exclusive events D
Before you start this chapter
1 What fraction of each shape is coloured?
a
b
4 True or false?
a 0.5 0.3 0.1 0.9
b 0.8 0.4 0.2 0.3
c 0.8 2 1.6
2 Work out each missing number.
a _17 _17 _17 __
7
b _29 __
_19 _59
9
3
c _47 _17 __
c
5 40
e 4
32
e 100% 66% 44%
f 18% 3 6%
3 Copy and complete.
a 67
d 75% 25% 100%
b 15 3 d 36 f
6
3 18
5 Find the next two terms in each sequence.
a _15 , _25 , _35 ,
,
10 __
6
b __
, 8 , __
,
10 10 10
,
HELP Chapter 3
7.1
The language of probability
Why learn this?
Probability helps
you understand your
chances of winning
the lottery.
Objectives
G Understand and use some of
the basic language of probability
Keywords
chance, likelihood,
probability, certain,
impossible
Skills check
1 What does the word ‘certain’ mean?
2 If something ‘might’ happen, does that mean it is ‘certain’ to
happen?
3 What does the word ‘impossible’ mean?
What is probability?
People often talk about the chance or likelihood that something might happen.
For example, ‘What is the chance that it will snow tomorrow?’
Probability is about measuring the likelihood that something might happen.
Some things are certain to happen.
For example, a baby will be born today.
Some things cannot happen.
For example, it is impossible that you will live until you are 180 years old.
Some things might happen.
For example, the next car you see might be red.
G
Example 1
Write down whether these things are certain to happen, might happen or are impossible.
a Newborn twins will both be boys.
b It will rain in Scotland next year.
c An athlete will run 100 m in two seconds.
a might happen
They might be both girls, or one girl and one boy.
b certain to happen
Scotland has a lot of rain every year.
c impossible
The current world record is 9.58 seconds.
Exercise 7A
G
Write down whether these things are certain to happen, might happen or are impossible.
1 The sun will rise tomorrow.
2 It will snow on New Year’s Day.
116
Probability 1
3 You will see a shooting star if you look at the sky tonight.
G
4 When you roll a normal dice you will roll a 7.
5 The next car to pass the school gates will be blue.
6 The day after Wednesday will be Thursday.
7 When you roll a dice you will roll a 6.
8 It will get dark tonight.
9 You will swim the length of a 25 m pool in 5 seconds.
10 In a litter of nine puppies, exactly half of them will be male.
7.2
L
Outcomes of an experiment
Why learn this?
Knowing all the
possible outcomes
helps you predict your
chances of success.
Objectives
G List all possible outcomes for an
experiment
Keywords
experiment, event,
outcome,
possible outcomes,
combined events
F List all possible outcomes for a combined event
Skills check
1 When you flip a coin, what could happen?
2 When you roll a dice, what could happen?
Writing outcomes
An experiment is something you do to find out what happens.
Rolling a dice is an experiment. In probability it is also called an event.
An experiment (or event) has outcomes. When you roll a dice you might get a 3.
So 3 is one of the possible outcomes of this event.
The event ‘rolling a dice’ has six possible outcomes, 1, 2, 3, 4, 5 or 6.
To write a list of outcomes, work systematically to make sure that you don’t miss any out.
When two things happen at the same time, such as rolling a dice and flipping a coin, they are
called combined events.
7.2 Outcomes of an experiment
117
G
Example 2
a An odd number is chosen from the numbers 1 to 10. List all the possible outcomes.
b A 10p coin and a 5p coin are flipped at the same time. List all the possible outcomes.
F
c A coin and a four-sided dice, numbered 1, 2, 3 and 4, are flipped at the same time.
List all the possible outcomes.
a 1, 3, 5, 7, 9
b HH, HT, TH, TT
c H1, H2, H3, H4,
T1, T2, T3, T4
List the numbers in order so you don’t miss
any out.
H stands for Head and T stands for Tail, so HT
means Head and Tail.
H1 means a Head on the coin and a 1 on the dice.
There are 8 possible outcomes altogether.
Exercise 7B
G
1 A coin is flipped. List all the possible outcomes.
2 A normal six-sided dice is rolled. List all the possible outcomes.
3 This spinner has three equal sectors coloured yellow, orange and pink.
The spinner is spun. List all the possible outcomes.
4 One item is selected from a bag containing 1 apple, 1 orange, 1 banana and 1 pear.
List all the possible outcomes.
5 This is the list of vegetables available in a school canteen.
Bryoni chooses two different vegetables.
List all the possible combinations of vegetables
that Bryoni could choose.
Today’s
vegetables
Broccoli
Carrots
Peas
Sweetcorn
6 Alison, Bethany, Christine, David and Eddie go to a dance together.
One of the girls must dance with one of the boys.
List all the possible combinations of dance partners.
F
7 Sam has a spinner, a coin and a normal six-sided dice.
The spinner has four equal sectors coloured red, blue, purple
and yellow.
a Sam flips the coin and spins the spinner at the same time.
List all eight possible outcomes.
b Sam flips the coin and rolls the dice at the same time.
List all 12 possible outcomes.
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118
c Sam spins the spinner and rolls the dice at the same time.
Without writing them all down, work out how many possible outcomes there are.
Explain how you worked out your answer.
Probability 1
8 A triangular spinner has sections labelled 1, 2 and 3.
A circular spinner has sections labelled 1 and 2.
The spinners are spun at the same time.
The numbers that the spinners land on are added to
give the score.
List all the possible scores.
F
1
2
1
3
2
9 The numbers on these two spinners have been rubbed out.
When the spinners are spun at the same time, the numbers
that the spinners land on are added to give the score.
The possible scores are 4, 6, 8 and 10.
What could the numbers on the spinners be?
?
?
?
?
?
L
NA F
NCTIO
NA
U
U
NCTIO
10 Glyn is organising a 5-a-side football tournament for a PE lesson.
25 pupils have been put into five teams, A, B, C, D and E.
Each team must play all the other teams.
The results will be put into a league table.
List all the combinations:
A v B, A v C etc.
a How many games will be played?
L F
The lesson lasts 75 minutes.
Glyn estimates there will be 1 minute intervals between games.
At the end, putting the results into a league table to decide the winners will take
about 6 minutes.
b How many minutes should Glyn allow for each game?
(All games must be the same length.)
7.3
L
The probability scale
Why learn this?
The probability
scale helps give
accurate measures of
probability.
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Keywords
Objectives
G Understand and use the basic
language of probability
probability scale, unlikely,
even chance, likely, fair
F Understand, draw and use a probability scale from 0 to 1
Skills check
1 Write these in order, starting with the smallest.
1
2
3
4
1
1
4
0
2 What fraction of each shape is yellow?
HELP Section 3.5
Probability in numbers and words
Probability uses numbers and words to describe
impossible unlikely
the chance that an event will happen.
1
0
It is measured on a probability scale from 0 to 1.
4
even
chance
likely
certain
1
2
3
4
1
Probability 0 means that the event cannot happen – it is impossible.
Probability 1 means that the event is certain to happen.
7.3 The probability scale
119
G
Example 3
a Use words to describe the probability of getting a head when a fair coin is flipped.
b What is the probability of getting a tail when a fair coin is flipped?
F
A coin is fair if
each outcome is
equally likely.
c Use words to describe the probability that the sun will rise tomorrow.
d What is the probability that the sun will rise tomorrow?
e Which colour is this spinner most likely to land on?
f What is the probability that this spinner will land on blue?
a even chance
The coin has 1 head and 1 tail.
1
b __
2
Even chance means the probability is _12 .
c certain
The sun will always rise.
d 1
Certain means the probability is 1.
e red
_3 of the spinner is red, so ‘red’ is likely.
1
f __
4
_1 of the spinner is blue, so ‘blue’ is unlikely.
4
4
Exercise 7C
G
1 Choose a word from the box below that describes the probability of each event
happening.
impossible
unlikely
even chance
likely
certain
a The sun will set tomorrow.
b Picking out a diamond from a shuffled pack of cards.
c Rolling an ordinary dice and getting a 9.
d A new born baby will be a boy.
In a pack of
cards there are
diamonds, hearts,
clubs and spades.
e Your birthday in 2020 will be on a Friday.
f
G
You will play a computer game tonight.
2 Write down two events of your own that would have a probability of ‘unlikely’.
3 Write down two events of your own that would have a probability of ‘certain’.
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120
4 Write down two events of your own that would have a probability of ‘impossible’.
Probability 1
a
5 Copy this probability
G
scale with arrows.
0
1
4
1
2
1
3
4
Label each arrow with an event from the list below. The first one is done for you.
a Picking the ace of hearts from the four aces in a pack of cards.
b It will rain in Glasgow next year.
c Flipping a coin and getting a tail.
A, E, I, O, U
are the
vowels.
d You will meet a famous movie star next Monday.
e Picking a letter from the word TENBY, and the letter is a vowel.
6 Draw a probability scale. Put an arrow on the scale to show the probability of each
G
of these events happening.
a The next car you see will be red.
b It will rain tomorrow.
c You will have maths homework next week.
d Picking a letter from the word ABERDEEN, and the letter is a vowel.
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e Picking out an ace from a shuffled pack of cards.
7 Copy this probability scale with arrows.
F
Work out the probability of each of these
spinners landing on red.
0
Label each arrow with the letter for
each spinner.
a
b
c
1
4
d
1
2
1
3
4
e
8 A fair six-sided spinner is numbered from 1 to 6.
The spinner is spun once.
Copy this probability scale. Put an arrow on the scale to
show the probability of each of these outcomes.
2
1
3
4
0
1
6
5
a The spinner lands on an odd number.
b The spinner lands on 1 or 2.
c The spinner lands on a number greater than zero.
9 Copy this spinner. Shade it so that the probability
of landing on a shaded section is _12 .
10 Copy this spinner. Use red, blue and yellow to
colour your spinner so the probability of landing
on red is _14 .
F
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7.3 The probability scale
121
7.4
Calculating probabilities
Why learn this?
Is it fair to flip a coin
to decide which team
starts the match?
Objectives
F Find the probability of an
outcome
Keywords
successful, possible
Skills check
1 True or false?
a _24 _12
3
b _15 __
15
4
1
c ___
__
100
50
2
1
d __
__
20
10
2 In a normal pack of playing cards
a How many spades are there?
b How many Kings are there?
c How many picture cards are there?
3 Copy and complete this table.
Fraction
Decimal
HELP Section 4.3
Percentage
1
__
10
50%
_3
4
0.8
Working out the probability
The probability of an event happening is
number of successful outcomes
Probability _____________________________
total number of possible outcomes
F
Example 4
a What is the probability of rolling a 4 on a fair six-sided dice?
b What is the probability of picking the Jack of diamonds from a shuffled pack of cards?
c You have 10 raffle tickets. 300 raffle tickets have been sold in total.
What is the probability that you will win?
122
1
a __
6
There is one 4 on a dice.
There are six numbers on the dice altogether.
1
b ___
52
There is one Jack of diamonds in a pack of cards.
There are 52 cards in the pack altogether.
10
c _____
300
Any one of your 10 tickets could win.
There are 300 tickets altogether.
Probability 1
Exercise 7D
1 A fair six-sided dice is rolled. Work out the probability of
a rolling a 1
c rolling an even number
b rolling a 2
d rolling a 12.
F
2 300 Christmas raffle tickets are sold. What is the probability of winning the raffle if
a
b
c
d
e
you have one ticket
you have five tickets
you have ticket number 7
you have tickets numbered 253 and 254
you forget to buy a ticket?
3 Alan bought 5 tickets for a school raffle.
5
.
The probability of Alan winning the raffle is ___
500
a How many raffle tickets were sold?
b Did Alan have ticket number 5?
c Alan’s Mum gives him two more tickets.
What is the probability of Alan winning the raffle now?
4 Hitesh buys three charity raffle tickets. Altogether 100 tickets will be sold.
1
.
Hitesh wants to make his probability of winning __
10
How many more tickets does he need?
7.5
L
Events that can happen in
more than one way
Why learn this?
You can work out the
probability of winning
a bet.
Objectives
F Work out the probability of an event
that can happen in more then one way
Skills check
1 Write each fraction in its simplest form.
6
15
2
12
a __
b __
c __
d __
15
10
12
20
2 Write down all the factors of 52.
How many ways can it happen?
Some events can happen in more than one way.
For example, if you wanted to pick an ace from a pack of cards, there are four ways this
could happen.
You could get the ace of spades, the ace of hearts, the ace of clubs or the ace of diamonds.
7.5 Events that can happen in more than one way
123
F
Example 5
A card is picked at random from an ordinary pack of playing cards.
What is the probability that the card is
a an ace
b a King
c a red card?
There are 4 aces in a pack.
There are 52 cards in the pack altogether.
4
a ___
52
4
4÷4
1
b ___ = ________ = ___
52
52 ÷ 4
13
There are 4 Kings in the pack of 52 cards.
4
1
__
cancels down to __
.
52
13
26
26 ÷ 26
1
c ___ = _________ = __
52
52 ÷ 26
2
A red card could be a diamond or a heart.
In a pack of cards, _12 are red and _12 are black.
Exercise 7E
F
1 A card is picked at random from an ordinary pack of
Picture cards
include all of the
Jacks, Queens and
Kings.
playing cards. What is the probability that the card is
a a Jack
b a Queen
c a picture card?
2 Anton rolls a fair six-sided dice.
‘At least 4’ means
you must include
the 4.
What is the probability that he rolls a number that is
a greater than 4
b less than 4
c at least 4?
3 Lucy has ten raffle tickets.
Altogether 500 raffle tickets have been sold.
What is the probability that
a Lucy wins the raffle?
b the winning ticket is a number greater than 400?
4 This fair spinner is spun.
What is the probability that it lands on an odd number?
1
4
5 One letter is chosen at random from the word
P R O B A B I L ITY
a the letter B
b a vowel
c made up entirely of straight lines.
124
Probability 1
3
8
7
Work out the probability that the letter is
2
The vowels are
A, E, I, O, and U
6
5
6 Lily has a bag containing 10 sweets.
Three are strawberry, one is cherry and six are raspberry flavour.
Lily takes one sweet from the bag at random.
Copy the probability scale below. Put an arrow on the scale to show the probability
of each of these outcomes.
0
F
1
a The sweet is strawberry flavour.
b The sweet is cherry flavour.
c The sweet is raspberry flavour.
7 Aster has a bag containing eight counters. Six of the counters are blue and two are red.
Aster takes a counter from the bag at random.
Draw a probability scale. Put an arrow on the scale to show the probability of each
of these outcomes.
F
a The counter is blue.
b The counter is red.
c The counter is orange.
8 Margery has three bags of counters. The bags contain red, blue and yellow counters.
A
B
C
a Which two bags should Margery mix together to give her the highest probability
of picking a red counter from the mixed bag?
b Margery mixes together the two bags from part a.
What is the probability that she picks a red counter at random from this
mixed bag?
9 Franz has three bags of counters. The bags contain red, blue and yellow counters.
Franz mixes two of the bags together.
A
B
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F
C
Franz says ‘If I mix bags B and C together, I have the best chance of picking out
a red counter. This is because in the mixed bag there are fewer blue and yellow
counters than red counters’. Explain why Franz is wrong.
10 Eve bought 4 raffle tickets. Pete said ‘400 tickets have been sold altogether’.
Later Eve bought another raffle ticket. Pete said ‘Now 500 tickets have been sold
altogether’.
Eve said ‘Oh no! I had more chance of winning when I had 4 tickets and only 400
tickets had been sold’. Explain why Eve is wrong.
7.5 Events that can happen in more than one way
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125
7.6
The probability that an event
does not happen
Why learn this?
If you know the
probability it won’t rain,
you can decide whether
to take an umbrella.
Skills check
1 Work out
2 Work out
3 Work out
Keywords
probability, event,
not, random
Objectives
E Work out the probability of an eventt not h
happening
appeniing
when you know the probability that it will happen
a 1 0.2
a 100% 30%
a 1 _13
b 1 0.75
b 100% 92%
b 1 _35
Calculating the probability that an event does
not happen
When you know the probability that an event will happen, you can calculate the probability
that the event will not happen by using this fact:
Probability that an event
1 Probability that the event
will not happen
will happen
(
E
)
(
)
Example 6
4
a The probability of picking an ace from a pack of cards at random is __
.
52
What is the probability of picking a card that is not an ace?
b The probability of picking a heart from a pack of cards at random is 0.25
What is the probability of picking a card that is not a heart?
E
48
12
a ___ = ___
52
13
52
48
4
4
1 __
__
__
__
52
52
52
52
b 0.75
1 0.25 0.75
Exercise 7F
1
1 The probability of picking a King from a pack of cards is __
.
13
What is the probability of picking a card that is not a King?
2 Hamish is learning to play golf.
1
.
The probability that he hits the ball in the right direction is __
10
What is the probability that his next shot
a goes in the right direction
b doesn’t go in the right direction?
126
Probability 1
Picking at random
means that each
card is equally
likely to be picked.
3 The probability that this spinner lands on 1 is 0.7
The probability that this spinner lands on blue is 0.85
What is the probability that the spinner
E
1
2
a does not land on 1
3
b does not land on blue?
4 The probability that this spinner lands on 1 is 28%.
The probability that this spinner lands on blue is 99%.
What is the probability that the spinner
3
a does not land on 1
b does not land on blue?
2
% means ‘out
of 100’
1
Catching the bus means
not missing the bus.
5 The probability that Hazel misses her bus is 0.05
What is the probability that Hazel catches her bus?
3
6 The probability of winning a £5 prize on the National lottery thunderball is ___
.
100
9
The probability of winning a £10 prize on the National lottery thunderball is ___
.
1000
Work out the probability of
a not winning a £5 prize
b not winning a £10 prize.
7 Alan buys a special spinner.
E
The spinner has sections numbered 1 to 5.
The probabilities of different scores are listed in the table.
a Work out the probability of
i not spinning a 1
ii not spinning a 3
iii not spinning a 5.
Number
Probability
1
2
3
4
0.3
0.2
0.25
0.25
b Explain what your answer to part iii means.
8 Sage has a biased dice numbered 1 to 6.
The probability of getting a 6 with this dice is _13 .
Sage says ‘There are 5 other numbers. So the probability of not
getting a 6 with this dice is _56 ’. Explain why Sage is wrong.
9 Leanne has a box that contains 20 counters.
Leanne picks a counter at random from the box.
The probability that she picks a blue counter is _45 .
a What is the probability that Leanne picks a counter
that is not blue?
With a biased dice,
outcomes are not
equally likely.
Picking at random
means that each
counter is equally
likely to be picked.
b How many counters in the box are not blue?
10 Lee has 10 coins in his pocket. He picks one at random.
The probability that Lee doesn’t pick a 10p coin is _25 .
How many 10p coins does Lee have in his pocket?
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E
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7.6 The probability that an event does not happen
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7.7
Mutually exclusive events
Why learn this?
It could help you win
if you remember what
cards have already
been played.
Skills check
1 Work out
2 Work out
a _15 _15
a 0.4 0.3
Keywords
Objectives
D Understand and use the fact that the
sum of the probabilities of all mutually
exclusive outcomes is 1
b 1 _14
b 1 0.82
mutually exclusive,
or, add, certain
c 1 _23
c 0.4 2
Mutually exclusive events
Mutually exclusive events cannot happen at the same time.
When you roll a dice you cannot get a 1 and a 6 at the same time.
When you flip a coin you can get either a head or a tail, but not both at the same time.
For any two events, A and B, which are mutually exclusive
P(A or B) P(A) P(B)
P(A) means the
probability of event A
occurring.
For a dice, the probability of rolling a 2 is _16
You can write this as P(2) _16
Also, P(1) _16 , P(3) _16 , P(4) _16 , P(5) _16 and P(6) _16
Add together the probabilities of all the possible outcomes:
P(1) P(2) P(3) P(4) P(5) P(6) _16 _16 _16 _16 _16 _16 1
This is because you are certain to roll either 1 or 2 or 3 or 4 or 5 or 6.
Rolling a 2 and not rolling a 2 are mutually exclusive events.
The total sum of their probabilities is _16 _56 1.
This is because you are certain to get either ‘2’ or ‘not 2’.
D
Example 7
a Work out the probability of rolling a 5 or a 6 with a fair dice.
b This spinner has four sections numbered 5 to 8.
The table shows the probability of the spinner landing on each number.
Number
Probability
5
6
7
8
0.2
0.2
0.2
?
5
8
6
7
What is the probability that the spinner lands on 8?
1
1
a P(5) = __, P(6) = __
6
6
2
1
1
1
__
__
P(5 or 6) = + = __ = __
6
6
6
3
b P(8) = 1 – 0.2 – 0.2 – 0.2
= 0.4
128
Probability 1
Work out P(5) and P(6).
Rolling a 5 and rolling a 6 are
mutually exclusive so add the
probabilities together.
Subtract the probabilities of 5, 6
and 7 from 1.
Exercise 7G
1 A box contains 15 chocolates.
Six of the chocolates have toffee centres, four are solid chocolate, three have soft
centres and two have nut centres.
One chocolate is taken from the box at random.
What is the probability that the chocolate
E
a doesn’t have a nut centre
b doesn’t have a toffee centre
c has a toffee or a chocolate centre
d has a toffee or a soft centre
D
e has a toffee or a nut centre
f
doesn’t have a toffee or a nut centre
g doesn’t have a soft or a nut or a toffee centre?
2 A tin contains biscuits.
One biscuit is taken from the tin at random.
The table shows the probabilities of taking each type of biscuit.
Biscuit
Probability
digestive
0.4
D
wafer
cookie
0.15
ginger
0.25
a What is the probability that the biscuit is a digestive or a cookie?
b What is the probability that the biscuit is a wafer?
3 A bag contains cosmetics.
One cosmetic is taken from the bag at random.
The table shows the probabilities of taking each type of cosmetic.
There are three times as many eyeshadows as blushers.
Cosmetic
Probability
eyeliner
0.3
lipgloss
0.3
D
eyeshadow
blusher
What is the probability that the cosmetic is an eyeshadow?
4 David puts 15 CDs into a bag.
Elliot puts 9 computer games into the same bag.
Fern puts some DVDs into the bag.
The probability of taking a DVD from the bag at random is _13 .
How many DVDs did Fern put in the bag?
7.7 Mutually exclusive events
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D
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129
Review exercise
It has the numbers 1 to 10 on it.
He rolls the dice once.
Work out the probability that Stefan
7
4
a rolls a 5
0
F
1 Stefan has this ten-sided dice.
[1 mark]
b rolls an even number
[1 mark]
c rolls a number greater than 6.
[1 mark]
2 A fair six-sided dice and a fair coin are thrown at
the same time.
The outcome T5 means a tail and a 5.
F
a Write a list of all the possible outcomes.
[1 mark]
b What is the probability of getting a tail and an odd number?
[1 mark]
c What is the probability of getting a head and a number less than three?
[1 mark]
3 Diego has two fair spinners.
Spinner A has four equal sections.
Two sections are blue, one is brown and the other is pink.
Spinner A
Spinner B
Spinner B has eight equal sections.
Three are blue, one is brown and four are pink.
Diego spins each spinner once.
a Which colour is spinner B most likely to land on?
[1 mark]
b Which spinner is more likely to land on brown, spinner A or spinner B?
Give a reason for your answer.
[1 mark]
c Copy this probability scale with arrows.
0
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F
E
130
1
Label each arrow with an event from the list below.
i Spinner A lands on blue.
ii Spinner A lands on pink.
iii Spinner B lands on brown.
iv Spinner B lands on blue.
[2 marks]
4 In a raffle 400 tickets are sold. There is only one prize.
Ruth buys 10 tickets, Penny buys 5 tickets, Holly and Lilly buy 3 tickets each.
a Which of the four girls has the best chance of winning the prize?
[1 mark]
b What is the probability that Penny wins the prize?
[1 mark]
c What is the probability that none of them wins the prize?
[1 mark]
Probability 1
5 A game of chance consists of turning over one card from each of two sets of cards.
The cards are
1
4
7
8
2
3
5
6
E
9
a The numbers on the cards are added together.
Complete this table to show all the possible outcomes.
Blue
Red
2
3
1
3
4
4
6
5
6
9
7
8
[2 marks]
b You win £1 if the total of your two cards is 10.
i What is the probability of winning?
ii What is the probability of not winning?
[1 mark]
[1 mark]
6 Alfie says ‘The probability that I don’t miss the bus in the morning is 0.85,
so the probability that I do miss the bus in the morning is 0.25’.
Is Alfie’s statement correct? Give a reason for your answer.
[1 mark]
E
AO2
7 A bag contains 36 marbles of three different colours, red (R), blue (B), and yellow (Y).
5
P(R) __
12
P(Y) _14
a Work out the probability of picking a blue marble.
b Work out the number of marbles of each colour in the bag.
[2 marks]
[3 marks]
D
AO2
Chapter summary
In this chapter you have learned how to
• understand and use the basic language of
probability G
• list all possible outcomes for an experiment G
• list all possible outcomes for a combined
event F
• understand, draw and use a probability scale
from 0 to 1 F
• work out the probability of an event that can
happen in more than one way F
• work out the probability of an event not
happening when you know the probability that
it will happen E
• understand and use the fact that the sum
of the probabilities of all mutually exclusive
outcomes is 1 D
• find the probability of an outcome F
Chapter 7 Summary
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