1. Probability Today you will need …… Orange Books Calculator Pen Ruler
Week 18
Today you will need ……
Orange Books
Calculator
Pen
Ruler
Complete your tracking sheet to evaluate your skills before the lesson

2. Chance, Likelihood, Evens, Certain, Impossible, Unlikely
What will you learn today? (something you did not know yesterday) By the end of this session I will be able to…
Show likelihood
Use fractions, decimals and percentages
Create a probability scale
Chance, Likelihood, Evens, Certain, Impossible, Unlikely
Key Words

3. What’s the difference between chance and probability?
Chance is described in words. Eg. Impossible, Unlikely, Evens, Likely, Certain Probability is given a numerical value. Probability is given as a fraction, decimal or percentage.

4. The rule of probability
𝑯𝒐𝒘 𝒎𝒂𝒏𝒚 𝒘𝒂𝒚𝒔 𝒕𝒉𝒆 𝒐𝒖𝒕𝒄𝒐𝒎𝒆 𝒚𝒐𝒖 𝒘𝒂𝒏𝒕 𝒄𝒂𝒏 𝒉𝒂𝒑𝒑𝒆𝒏 𝑻𝒐𝒕𝒂𝒍 𝒐𝒖𝒕𝒄𝒐𝒎𝒆𝒔
It is often easier to give a probability as a fraction using the rule above. Use your skills to convert into percentage or a decimal.

5. Here’s how the rule works:
A bag contains 9 blue marbles, 5 red marbles and 6 green marbles. What’s the probability of selecting a blue marble from the bag?
What you want:
How many blue marbles there are 9
Total outcomes:
How many marbles there are in total 20

6. More than one option
A bag contains 6 blue marbles, 5 red marbles and 9 green marbles. What’s the probability of selecting a green or red marble from the bag?
What you want:
How many green or red marbles there are 14
Total outcomes:
How many marbles there are in total 20

7. Colour
Probability
Chance
Red
Green
Colour
Probability
Chance
Red
Green
Blue
Colour
Probability
Chance
Red
Green
Blue

8. A four An even number More than a two A multiple of three
What is the probability of rolling ……
A four
An even number
More than a two
A multiple of three

9. What is a probability scale?
This is a line where events can be placed to show the chance or probability of an event occurring.
Impossible
Certain
3 4
1 4
1 2 1 0%
100%
25%
50%
75%

10. Tree diagrams.
If I roll a dice, what is the probability the result will be even?
3 6
3 ÷ 6 =
0.5
Even
Check the results add up to 1
= 1
Odd
3 6
3 ÷ 6 =
0.5

11. Combined outcomes 1 4 Suppose I toss two coins: or
I would get one of these combinations:
Heads, Heads Heads, Tails Tails, Heads Tails, Tails
H, H H, T T, H T, T or
What is the probability of getting two heads?
1 4
Only one of these four combinations is two heads

12. Sample Space Diagrams T, T T, H T H, T H, H H Second Coin First Coin
A Sample Space is a list of all the possible outcomes, e.g. HH, HT, TH, TT
T, T
T, H T
H, T
H, H H
Second Coin
First Coin
We can show the coin toss like this …
There are 4 possible outcomes if you toss both coins once
So the probability of two heads is ¼

13. Please don’t write on the worksheets
Individual Study
Choose which areas to develop depending on your own strengths and areas identified from your diagnostic
Computers available
Please don’t write on the worksheets

14. Reflection of the lesson Complete your tracking sheets
How do you now feel about todays topic
What did you learn new today?
What are your next steps?