Odds
Finding the Odds of an event
• When all outcomes are equally likely, the
ODDS that an event will occur is given by
the formula below:
Odds = Number of favorable outcomes
Number of of unfavorable outcomes
Ex. 4: Finding the odds of an event
• You randomly choose an integer from 0
through 9. What are the odds that the
integer is 4 or more?
Ex. 4: Finding the odds of an event
SOLUTION:
There are 6 favorable outcomes, 4, 5, 6, 7, 8,
and 9. There are four unfavorable outcomes
0, 1, 2, 3.
Odds = Number of favorable outcomes
Number of unfavorable outcomes
6 3
 
4 2
The odds that the integer is
4 or more are 3 to 2.
ODDS
If you know the probability that an event will
occur, you can find the odds.
Odds = Probability event will occur
Probability the event will not occur
Is equal to:
Probability event will occur
1 – (Probability event will occur)
Ex. 5: Finding Odds from probability
• The probability that a randomly chosen
household has a cat is 0.27. What are the
odds that a household has a cat?
Odds = Probability the event will occur
1 – (Probability the event will occur)
0.27
The odds are 27 to

Substitute for probabilities
73 that a randomly
1  0.27
chosen household
0.27

has a cat.
Simplify the denominator
0.73
27

Multiply numerator and denominator by 100 to get rid of decimals.
73