Lesson

Remember we can represent likelihood like a number line. We start with impossible events on the left and as we move right the events are more likely.

Which section describes the chance of 'the next person you meet has the same birthday as you'?

A

B

Worked Solution

Idea summary

These are terms we have seen to describe chance:

Impossible: definitely will NOT happen.

Unlikely: there is less than a 50\% chance of it happening.

Even chance: there is a 50\% chance of it happening.

Likely: there is more than a 50\% chance of it happening.

Certain: definitely will happen.

We have heard about certain and impossible events, this video shows how these can be represented using a number.

The events A, B, C and D have probabilities as shown on this probability line:

a

Which event could be 'flipping a coin and getting a tail'?

A

Event A

B

Event B

C

Event C

D

Event D

Worked Solution

b

Which event could be 'rolling a six-sided die and getting a number less than 11'?

A

Event A

B

Event B

C

Event C

D

Event D

Worked Solution

Idea summary

We can use a number to represent the probability of an event. A probability of 0 means the event is impossible, a probability of \dfrac{1}{2} means the event has an even chance, and a probability of 1 means the event is certain.

This video shows you how likelihoods can have fractional representation.

Event X has a probability of \dfrac{6}{10}.

a

If event X was placed on the number line, which section would it be placed in?

A

B

Worked Solution

b

What is the chance of event X occurring?

A

Certain

B

Likely

C

Unlikely

Worked Solution

Idea summary

We can use numbers as well as words to describe chance:

Words for chance | Numbers for chance |
---|---|

\text{Impossible} | 0 |

\text{Unlikely} | \text{A fraction between }0 \text{ and }\dfrac{1}{2} |

\text{Even} | \dfrac{1}{2} |

\text{Likely} | \text{A fraction between }\dfrac{1}{2} \text{ and }1 |

\text{Certain} | 1 |

This video looks at finding the probability of an event from a spinner.

Look at this spinner:

a

Complete the table, showing the probability of each outcome.

Worked Solution

b

What is the sum of the probabilities for each outcome?

Worked Solution

Idea summary

The probability of something happening can be written as a fraction. If there are 3 of what we want, out of a total of 10, then we have 3 chances out of 10 of it happening. As a fraction, it's \dfrac{3}{10}.

Describe probabilities using fractions, decimals and percentages