Page 214 - Math Course 3 (Book 2)

Probability of Compound Events

P(cat or dog) = P(cat) + P(dog) Definition of = 6 or 2 Simplify.
mutually exclusive 9 3
events
The probability of a puppy being
2
7 8 Answer male or mixed-color is or
= + Substitution 3
20 20 67%. The answer is D.

15 3 Add
= or
20 4

The probability of randomly Your Turn!
Answer 3
picking a cat or a dog is .
4
Mutually Exclusive Events

The French Club has 16 seniors, 12 juniors, 15
Standardized Test Example sophomores, and 21 freshmen as members.
What is the probability that a member chosen at
random is a junior or a senior?
PETS
A dog has just given birth to a litter of 9 puppies. A. 7
There are 3 brown females, 2 brown males, 1 16
mixed-color female, and 3 mixed-color males. If B. 1
you choose a puppy at random from the litter, what
is the probability that the puppy will be male or C. 9
mixed-color? 16
D. 0

Answer

Standardized Test Example

In Mrs. Kline’s class, 7 boys have brown eyes and
5 boys have blue eyes. Out of the girls, 6 have
brown eyes and 8 have blue eyes. If a student
2 1 5 2
A B C D is chosen at random from the class, what is the
9 3 9 3 probability that the student will be a boy or have
Since three of the puppies are both mixed-colored brown eyes?
and males, these events are inclusive. 5 9
A. B.
13 13
P(A or B) = P(A) + P(B) – P(A and B) Definition of
inclusive C. 7 D. 6
events 13 13
P(male or mixed-color) =
P(male) + P(mixed-color) – P(male and mixed-color)

Answer
5
4
= + – 3 Substitution
9 9 9 Substitution
= 5 + 4 – 3 LCD is 9.
9

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