Chance events
Use fractions to describe chance.
Lucky draws
In a raffle of 100 tickets, you have 1 ticket. Your chance of winning is 1 in 100. We can write probability as a fraction: 1/100.
Probability as a fraction
There are 4 equally likely sections. 2 are red, so P(red) = 2/4 = ½. P(green) = ¼.
The probability scale
All probabilities are between 0 and 1. P(rolling a 7 on a dice) = 0. P(rolling less than 7) = 1.
Counting outcomes
Count the outcomes you want (favourable). Divide by all possible outcomes. This works when outcomes are equally likely.
Tree diagrams and fair games
A tree diagram shows all outcomes: HH, HT, TH, TT. P(two heads) = 1 out of 4 = ¼. A game is fair if every player has the same chance of winning.
What I learnt
- I can write probability as a fraction.
- I can use the 0 to 1 scale.
- I can count outcomes.