Odds

1
9-8
Odds
Warm Up
Problem of the Day
Lesson Presentation
Pre-Algebra
2
Warm Up A bag contains 15 nickels, 10 dimes, and
5 quarters. Two coins are drawn without
replacement. 1. Find the probability that the
first is a dime and the second is a
quarter. 2. Find the probability that they are
both nickels.
3
Learn to convert between probabilities and odds.
Vocabulary
odds in favor odds against
4
The odds in favor of an event is the ratio of
favorable outcomes to unfavorable outcomes. The
odds against an event is the ratio of unfavorable
outcomes to favorable outcomes.
Odds are written in lowest terms!!!
a number of favorable outcomes
b number of unfavorable outcomes
a b total number of outcomes
5
In a club raffle, 1,000 tickets were sold, and
there were 25 winners. A. Estimate the odds in
favor of winning this raffle.
Favorable outcomes 25
Unfavorable outcomes 1000 25 975
Odds in favor 25 to 975
Odds in favor 1 to 39
6
In a club raffle, 1,000 tickets were sold, and
there were 25 winners. B. Estimate the odds
against winning this raffle.
Favorable outcomes 25
Unfavorable outcomes 1000 25 975
Odds against 975 to 25
Odds against 39 to 1
7
Of the 1750 customers at an arts and crafts show,
25 will win door prizes. A. Estimate the odds in
favor winning a door prize.
Favorable outcomes 25
Unfavorable outcomes 1750 25 1725
Odds in favor 25 to 1725
Odds in favor 1 to 69
8
A. If the odds in favor of winning a CD player
in a school raffle are 149, what is the
probability of winning a CD player?
P(CD player)
2
9
B. If the odds against winning the grand prize
are 11,9991, what is the probability of winning
the grand prize?
P(grand prize)

0.0083333
10
Odds Against
(n m) m
(10 1) 1
9 1
11
Odds Favor
m(n m)
1 (30 1)
1 29
(n m) m
Odds Against
(50 1) 1
49 1
12
Lesson Quiz
119
191
599,9991
13
Homework

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• 1 20 all, 27 33 all