When calculating a probability, we are comparing the number of positive outcomes to the number of possible outcomes. Calculating the odds O against an event occurring, however, is the ratio of negative outcomes to positive outcomes.
O=Negative Outcomes/Positive Outcomes
Now we can look at the spinner and find the number of positive and negative outcomes.
On the spinner we have numbers from 1 to 6.
1, 2, 3, 4, 5, 6
We want to find the odds against a factor of 6. In order to do that, we can rewrite 6 using factor pairs of 6.
Factor pairs
Number
1* 6
6
2* 3
6
There are 4 factors of 6. Therefore, the number of positive outcomes is 4. The number of negative outcomes is the number of sections in the spinner that are labeled with a number that is not a factor of 6. In this case, there are 2 negative outcomes.
1, 2, 3, 4, 5, 6
Now we know how many outcomes are positive and negative.
Positive:& 4
Negative:& 2
Let's form our ratio and then simplify it as much as possible.
