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Pre-Algebra 9-8 Odds Pre-Algebra HOMEWORK Page 480 #1-12 Turn in for Credit!
Pre-Algebra
9-8 Odds
Pre-Algebra HOMEWORK
Page 480
#1-12
Turn in for Credit!
Pre-Algebra
9-8 Odds
Pre-Algebra HOMEWORK
Page 484
#1-6
Due on MONDAY!
Pre-Algebra
9-8 Odds9-8 Odds
Pre-Algebra
Warm UpWarm Up
Problem of the DayProblem of the Day
Lesson PresentationLesson Presentation
Pre-Algebra
9-8 Odds
Warm UpA 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.
Pre-Algebra
9-8 Odds
587
729
Pre-Algebra
9-8 Odds
Problem of the Day
Larissa was born in August. What is the probability that she was born on an odd-numbered day? ≈ 0.52
Pre-Algebra
9-8 Odds
Today’s Learning Goal Assignment
Learn to convert between probabilities and odds.
Pre-Algebra
9-8 Odds
Vocabulary
odds in favorodds against
Pre-Algebra
9-8 Odds
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 in favor aa::bb
odds against bb::aa
aa = number of favorable outcomes
bb = number of unfavorable outcomes
a a ++ b b = total number of outcomes
Pre-Algebra
9-8 Odds
In a club raffle, 1,000 tickets were sold, and there were 25 winners.
A. Estimate the odds in favor of winning this raffle.
Additional Example 1A: Estimating Odds from an Experiment
The number of favorable outcomes is 25, and the number of unfavorable outcomes is 1000 – 25 = 975. The odds in favor of winning this raffle are about 25 to 975, or 1 to 39.
Pre-Algebra
9-8 Odds
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.
Try This: Example 1A
The number of favorable outcomes is 25, and the number of unfavorable outcomes is 1750 – 25 = 1725. The odds in favor of winning a door prize are about 25 to 1725, or 1 to 69.
Pre-Algebra
9-8 Odds
In a club raffle, 1,000 tickets were sold, and there were 25 winners.
B. Estimate the odds against winning this raffle.
Additional Example 1B: Estimating Odds from an Experiment
The odds in favor of winning this raffle are 1 to 39, so the odds against winning this raffle are about 39 to 1.
Pre-Algebra
9-8 Odds
Try This: Example 1BOf the 1750 customers to an arts and crafts show, 25 win door prizes.
B. Estimate the odds against winning a door prize at the show.
The odds in favor of winning a door prize are 1 to 69, so the odds against winning a door prize are about 69 to 1.
Pre-Algebra
9-8 Odds
Probability and odds are not the same thing, but they are related. Suppose you want to know the probability of rolling a 2 on a fair die. There is one way to get a 2 and five ways not to get a 2, so the odds in favor of rolling a 2 are 1:5. Notice the sum of the numbers in the ratio is the denominator of the probability . 1
6
Pre-Algebra
9-8 Odds
A. If the odds in favor of winning a CD player in a school raffle are 1:49, what is the probability of winning a CD player?
Additional Example 2A: Converting Odds to Probabilities
On average there is 1 win for every 49 losses, so someone wins 1 out of every 50 times.
P(CD player) =1501 + 49
1=
Pre-Algebra
9-8 Odds
Try This: Example 2A
A. If the odds in favor of winning a bicycle in a raffle are 1:75, what is the probability of winning a bicycle?
On average there is 1 win for every 75 losses, so someone wins 1 out of 76 times.
P(bicycle) =1761 + 75
1=
Pre-Algebra
9-8 Odds
B. If the odds against winning the grand prize are 11,999:1, what is the probability of winning the grand prize?
Additional Example 2B: Converting Odds to Probabilities
P(grand prize) =
If the odds against winning the grand prize are 11,999:1, then the odds in favor of winning the grand prize are 1:11,999.
1 + 11,999 1 =
12,0001
≈0.000083333
Pre-Algebra
9-8 Odds
B. If the odds against winning the grand prize are 19,999:1, what is the probability of winning the grand prize?
Try This: Example 2B
P(grand prize) =
If the odds against winning the grand prize are 19,999:1, then the odds in favor of winning the grand prize are 1:19,999.
1 + 19,999 1 =
20,0001
≈ 0.00005
Pre-Algebra
9-8 Odds
Suppose that the probability of an event is . This means that, on average, it will happen in 1 out of every 3 trials, and it will not happen in 2 out of every 3 trials, so the odds in favor of the event are 1:2 and the odds against the event are 2:1.
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CONVERTING PROBABILITIES TO ODDS
If the probability of an event is , then the odds in
favor of the event are m:(n – m) and the odds
against the event are (n – m):m.
mn
Pre-Algebra
9-8 Odds
Additional Example 3: Converting Probabilities to Odds
On average, 1 out of every 20 people wins, and the other 19 people lose. The odds in favor of winning the meal are 1:(20 – 1), or 1:19.
On average, 1 out of every 10 people wins, and the other 9 people lose. The odds against the door prize are (10 – 1):1, or 9:1.
A. The probability of winning a free dinner is . What are the odds in favor of winning a free dinner?
120
B. The probability of winning a door prize is . What are the odds against winning a door prize?
110
Pre-Algebra
9-8 Odds
Try This: Example 3
A. The probability of winning a free laptop is . What are the odds in favor of winning a free laptop?
130
On average, 1 out of every 30 people wins, and the other 29 people lose. The odds in favor of winning the meal are 1:(30 – 1), or 1:29.
On average, 1 out of every 50 people wins, and the other 49 people lose. The odds against the door prize are (50 – 1 ):1, or 49:1.
B. The probability of winning a math book is . What are the odds against winning a math book?
150
Pre-Algebra
9-8 Odds
Lesson Quiz
19:1
1:19
599,999:1
1900
Of 200 people at the grand opening of a store, 10 will win door prizes.
1. Estimate the odds of winning a door prize.
2. Estimate the odds against winning a door prize.
3. If the odds of winning a new computer are 1:899, what is the probability of winning the computer?
4. The probability of winning a new truck is . What are the odds against winning the truck?
1600,000
