2. Learning Intentions
• Understand what is meant by probability.
• How to express probability on a probability scale.
• How to express probability as a fraction or percentage.
3. P RO B A B I L I T Y
Probability is how likely something is to happen.
• If something has a low probability, it is unlikely to happen
• If something has a high probability, it is likely to happen
Probabilities can be written in words but are more commonly written
as fractions or decimals.
4. P RO B A B I L I T Y
Words to describe
probability
certain
impossible
Very unlikely
likely
Very likely
Even chance
unlikely
50/50
5. P RO B A B I L I T Y
even chance
50/50
Impossible certain
Very
unlikely
unlikely likely
Very
likely
6. P RO B A B I L I T Y
even chance
50/50
Impossible certain
Very
unlikely
unlikely likely
Very
likely
How likely is it that it will rain next week?
How likely is it that it will be Tuesday tomorrow?
How likely is it that you will put up a Christmas tree today?
How likely is it that a coin will land on heads when you throw it?
7. P RO B A B I L I T Y A S A F R AC T I O N
First work out how many times the event has occurred or could occur.
Second, work out the total number
Write them as a fraction with the bigger number on the bottom.
For example, what is the probability of landing on purple?
1/5
8. P RO B A B I L I T Y A S A F R AC T I O N
What is the probability of landing on green?
3
/12 = ¼
What is the probability of landing on red?
5
/12
What is the probability of landing on blue or yellow?
4
/12 = 1
/3
9. P RO B A B I L I T Y A S A F R AC T I O N
Think of a fair dice with 6 sides and 6 different numbers
What is the probability of landing on a 4?
What is the probability of landing on an even number?
What is the probability of landing on a number greater than 4?
11. Learning Intentions
• Understand what is meant by probability.
• How to express probability on a probability scale.
• How to express probability as a fraction or percentage.
