Warm Up ...
How many different outfits can you create
if you have three shirts and four pairs of
shorts?
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13.1
Finding
Probabilities
& Odds
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Important Vocab:
1. Outcome: possible results of an
experiment
2. Event: outcome, or collection of
outcomes
3. Sample Space: set of all
possible outcomes
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Example: You flip a coin and roll a six sided
number cube. How many possible outcomes
are in the sample space? List the possible
outcomes.
4
You Try!
You flip a coin twice. How many possible
outcomes are in the sample space? List the
possible outcomes.
5
You Try!
You flip two coins and roll a six sided number
cube. How many possible outcomes are in
the sample space? List the possible
outcomes.
6
4. Probability of an Event: measure of the
likelihood, or chance, that the event will
occur
* probability is a number from 0 to 1 and can
be expressed as a decimal, fraction, or
percent
P=0
Impossible
P = 0.25
Unlikely
P = 0.5
Equally likely to
happen or not happen
P = 0.75
Likely
P=1
Certain
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5. Favorable Outcomes: outcomes for a specific event
6. Theoretical Probability:
theoretical probability =
number of favorable outcomes
total number of outcomes
probability of event A is written P(A)
8
You and your friends designed t­shirts with silk screened
emblems, and you are selling the t­shirts as a fundraiser. The
table below shows the number of t­shirts you have in each
design. A student chooses a t­shirt at random. What is the
probability that the student chooses a red t­shirt?
Gold Emblem
Silver Emblem
Green T­Shirt
10
8
Red T­Shirt
6
6
What is the probability that the student chooses a
T­Shirt with a gold emblem?
What is the probability that the student chooses
a red T­Shirt with a gold emblem?
9
A department store is offering a discount on sunglasses. The
table shows the number of each type of sunglasses. You
choose a pair at random. What is the probability that the pair
you choose is polarized?
Green Lens
Brown Lens
Polarized
8
4
Mirrored
7
9
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7. Trial: number of times an experiment is performed
8. Success: number of times in which a favorable
outcome occurs
9. Experimental Probability:
experimental probability =
Number of Successes
Number of Trials
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12
Each section of the spinner has
the same area. The spinner was
spun 20 times. The table shows
the results. For which color is the
experimental probability of
stopping on the color the same as
the theoretical probability?
Spinner Results
Red
5
Orange
9
Green
Blue
3
3
13
A bag contains one blue, one green, one yellow, and one red
ball. A ball is drawn at random from the bag and then replaced.
The table shows the results for 24 drawings. For which color of
ball is the experimental probability of drawing the color the
same as the theoretical probability?
Random Drawing Results
Red
Yellow
Green
Blue
4
6
9
5
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10. Odds: compare the number of favorable and
unfavorable outcomes when all outcomes are
equally likely
11. Odds in favor:
odds in favor =
Number of Favorable Outcomes
Number of Unfavorable Outcomes
12. Odds against:
odds against =
Number of Unfavorable Outcomes
Number of Favorable Outcomes
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Each section of the spinner has
the same area.
Finds the odds against stopping
on green.
Find the odds of landing on
orange.
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Classwork:
page 846: 4, 10, 12
Homework:
page 846: 3 ­ 19, 20, 21 odd (skip 17)
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