Probability
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MNU 3-22a
MNU 4-22a
Probability in Ratio Form
Probability in Fraction Form
Independent Events (Extension)
Dependent Events (Extension)
14-Jul-17
Created by Mr. Lafferty Maths Dept.
Starter Questions
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MNU 3-22a
MNU 4-22a
1.
Find the value of x if
4x=48
o
47
o
55
xo :
x
o
2.
Calculate
3.
Change 23.3km to m
4.
Find the average of the numbers 15, 25, 20?
14-Jul-17
Created by Mr. Lafferty Maths Dept.
Probability
www.mathsrevision.com
MNU 3-22a
MNU 4-22a
Learning Intention
Success Criteria
1. We are learning how to
calculate probability in
ratio form.
1. Understand the term
probability.
2. Calculate the probability
of an event happening.
3. Write in ratio form.
14-Jul-17
Created by Mr. Lafferty Maths Dept.
Which event is fair?
Tossing a coin
Likelihood Line
MNU 3-22a
MNU 4-22a
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Probability
0
Impossible
It will
Snow in winter
14-Jul-17
0.5
Not very
likely
Evens
Homework Everyone getting
Every week
100 % in test
Created by Mr. Lafferty Maths Dept.
1
Very
likely
Certain
Toss a coin Going without
That land
Food
Heads
for a year.
Probability
Calculating Ratio Probability
MNU 3-22a
MNU 4-22a
www.mathsrevision.com
One way of thinking about Probability is as a ratio
Chance of an event happening is
1 in .........
P(Event) = the number of favourable events
compared to the total number of events.
14-Jul-17
Created by Mr. Lafferty Maths Dept.
Probability
Calculating Ratio Probability
MNU 3-22a
MNU 4-22a
www.mathsrevision.com
Example : What is the chance of getting a 4 when rolling a dice.
The number of favourable events is 1
The number of total events is 6
So probability is
P(4) = 1 in 6 chance
14-Jul-17
Created by Mr. Lafferty Maths Dept.
(1,2,3,4,5,6,)
Probability
Calculating Ratio Probability
MNU 3-22a
MNU 4-22a
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Example : What is the chance of getting an odd when rolling a dice.
The number of favourable events is 3
The number of total events is 6
(1,2,3,4,5,6,)
So probability is
Simplify
HCF = 3
14-Jul-17
P(odd) = 3 in 6 chance
P(odd) = 1 in 2 chance
Created by Mr. Lafferty Maths Dept.
(1,3,5)
Probability
Calculating Ratio Probability
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MNU 3-22a
MNU 4-22a
Now try TJ3b
Ex 2
Ch13 (page 140)
14-Jul-17
Created by Mr. Lafferty Maths Dept.
Starter Questions
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MNU 3-22a
MNU 4-22a
1.
Find the value of x if
5x - 5 = 45
2.
Change 6.7cm to mm
3.
What is probability ?
14-Jul-17
Created by Mr. Lafferty Maths Dept.
Probability
www.mathsrevision.com
MNU 3-22a
MNU 4-22a
Learning Intention
Success Criteria
1. We are learning how to
calculate probability in
fraction form.
1. Understand the term
probability.
2. Calculate the probability
of an event happening.
3. Write in fraction form.
14-Jul-17
Created by Mr. Lafferty Maths Dept.
Probability
Calculating Probability
MNU 3-22a
MNU 4-22a
www.mathsrevision.com
Probability can be thought of as a simple fraction or decimal.
It always lies between 0 and 1.
0 meaning impossible ( could not happen)
1 meaning certain ( will definitely happen)
Probability of an event happening =
14-Jul-17
number of favourable outcomes
number of possible outcomes
Created by Mr. Lafferty Maths Dept.
Probability
Calculating Probability
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MNU 3-22a
MNU 4-22a
Example : A boy tossed a coin.
What is the probability that it is heads.
1
P( H ) 
2
Example : There are 3 red and 4 green balls in a bag.
What is the probability a green ball is picked.
4
4
P(G) 

3 4 7
14-Jul-17
Created by Mr. Lafferty Maths Dept.
Probability
www.mathsrevision.com
MNU 3-22a
MNU 4-22a
Now try TJ3b
Ex 3
Ch13 (page 141)
Are you on Target ?
I can ?
14-Jul-17
Created by Mr. Lafferty Maths Dept.
Starter Questions
www.mathsrevision.com
MNU 3-22a
MNU 4-22a
1.
Find the value of x if
3x =123
o
62
2.
Calculate x o :
3.
Change 53cm to m
4.
Calcuate the probability of
picking an ace from a set of playing cards.
14-Jul-17
o
70
x
o
Created by Mr. Lafferty Maths Dept.
Probability
www.mathsrevision.com
MNU 3-22a
MNU 4-22a
Learning Intention
Success Criteria
1. We are learning how to
calculate probability for
independent events.
14-Jul-17
1. Understand the independent
event.
2. Calculate the probability
of independent event.
Created by Mr. Lafferty Maths Dept.
Probability
Calculating Probability
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MNU 3-22a
MNU 4-22a
Independent events are events that do not depend on each other.
Example :
Landing a tails when flipping a coin and
Rolling a 5 on a dice.
Example :
Choosing a Jack from a set of playing cards,
replacing it, and then choosing a 7.
P(E1 and E2) = P(E1) x P(E2)
14-Jul-17
Created by Mr. Lafferty Maths Dept.
Probability
Calculating Probability
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MNU 3-22a
MNU 4-22a
Example : What is the probability of tossing a coin and getting
a heads and then tossing again and getting another heads.
P(H) =½
P(H) =½
P(E1 and E2) = ½ x ½ = ¼
Example : There are 3 red and 1 green balls in a bag.
What is the probability of picking a green ball,
replacing it and then picking a red ball.
P(G) =¼
P(R) =¾
14-Jul-17
P(E1 and E2) = ¼ x ¾ =
Created by Mr. Lafferty Maths Dept.
3
16
Probability
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MNU 3-22a
MNU 4-22a
Now try TJ3b
Ex 4
Ch13 (page 146)
14-Jul-17
Created by Mr. Lafferty Maths Dept.
Starter Questions
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MNU 3-22a
MNU 4-22a
1.
Find the value of x if
2x - 1 = 49
o
xo
72
2.
Calculate
3.
Calcuate the probability of
picking an ace replacing it
and then picking a five.
14-Jul-17
o
x
57
o
Created by Mr. Lafferty Maths Dept.
Probability
www.mathsrevision.com
MNU 3-22a
MNU 4-22a
Learning Intention
Success Criteria
1. We are learning how to
calculate probability for
dependent events.
14-Jul-17
1. Understand the dependent
event.
2. Calculate the probability
of dependent event.
Created by Mr. Lafferty Maths Dept.
Probability
Calculating Probability
MNU 3-22a
MNU 4-22a
www.mathsrevision.com
Dependent events are events that affect the next event.
Example :
Choosing a Jack from a set of playing cards,
WITHOUT REPLACING IT then picking a three.
P(E1 and E2) = P(E1) x P(E2)
14-Jul-17
Created by Mr. Lafferty Maths Dept.
Probability
Calculating Probability
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MNU 3-22a
MNU 4-22a
Example : There are 3 yellow and 2 blue balls in a bag.
What is the probability of picking a blue ball,
NOT replacing it, and then picking a yellow ball.
P(Blue) =
P(Yellow) =
14-Jul-17
2
5
3
P(B and Y) =
4
Created by Mr. Lafferty Maths Dept.
2
5
x
3
4
=
6
20
=
3
10
Probability
Calculating Probability
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MNU 3-22a
MNU 4-22a
Example : What is the probability of choosing a diamond from a set
of playing cards, NOT replacing it, and then picking
another diamond.
P(◊) =
P(◊) =
14-Jul-17
13
52
12
51
P(◊ and ◊) =
13
52
x
Created by Mr. Lafferty Maths Dept.
12
51
=
156
2652
=
3
51
Have you updated
your Learning Log ?
Probability
www.mathsrevision.com
MNU 3-22a
MNU 4-22a
Now try TJ3b
Ex 5
Ch13 (page 147)
Are you on Target ?
I can ?
14-Jul-17
Created by Mr. Lafferty Maths Dept.