1. Lesson 1

1.6. Explore 2

Mathematics 30-2 Module 2

Module 2: Probability

 

In Share 2, a few different relationships were observed.

 

You saw that the probability of winning added to the probability of not winning equals 1. The formula used to describe the probability of an event and its complement is .

 

In the case of the door prizes, it would look like this:

 

 

 

In Try This 2 you used the odds formula to find the odds of winning and the odds against winning as fractions and ratios:

 

 

 

 

Or

 

 

odds in favour of A = number of outcomes for A : number of outcomes against A

 

You may have also noticed the relationship between the odds of winning and the odds against winning:

 

  • odds for winning → 2 : 3
  • odds against winning → 3 : 2

Notice how the ratio for the odds is reversed.


You may also have noticed the connection between probability and odds. Probability is based on winning a prize out of all of the possibilities, whereas odds are based on winning a prize compared to not winning a prize.

 

The difference between odds and probability is this:

  • Probability is based on favourable outcomes in relation to the total number of possible outcomes.
  • Odds are based on the favourable outcomes “for” in relation to unfavourable outcomes “against.”