Page 213 - Math Course 3 (Book 2)

Probability of Compound Events

MO. 12 - L7b Mutually Inclusive Events

Mutually Exclusive or Inclusive Words If two events, A and B, are inclusive,

Events then the probability that either A or B
occurs is the sum of their probabilities
decreased by the probability of both
occurring.
Vocabulary A-Z Symbols P(A or B) = P(A) + P(B) – P(A and B)

Let us learn some vocabulary Model

complement A B
The complement is everything else that could
happen other than the event or proposition in
question.
P
P (sum of P (A or B)
P(green) (not green) probabilities)

11 + 27 = 1 Let’s Begin
38 38

The probability of the event of proposition and its
complement must add up to 1. Mutually Exclusive Events

mutually exclusive Example
Events that cannot occur at the same time are
called mutually exclusive.
Suppose you want to find the Alfred is going to the Lakeshore Animal Shelter to
probability of rolling a 2 or a pick a new pet. Today, the shelter has 8 dogs, 7
4 on a die. Since a die cannot cats, and 5 rabbits available for adoption. If Alfred
show both a 2 and 4 at the randomly picks an animal to adopt, what is the
same time, the events are probability that the animal would be a cat or a dog?
mutually exclusive.

Key Concept

Mutually Exclusive Events

Words If two events, A and B, are mutually
exclusive, then the probability that
either A or B occurs is the sum of their
probabilities. Since a pet cannot be both a dog and a cat, the
events are mutually exclusive.
Symbols P(A or B) = P(A) + P(B)

7 ← number of cats
Model P(cat) =
20 ←total number of pets
A B ← number of dogs

P(dog) = 8
20 ←total number of pets
P
(A or B)
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