Transcript What you really need to know!

Lesson 9-7 Pages 398-401
Independent and
Dependent
Events
What you will learn!
How to find the probability
of independent and
dependent events.
Compound event
Independent event
Dependent event
What you really need to know!
A compound event
consists of two or
more simple events.
What you really need to know!
The probability of two
events can be found by
multiplying the probability
of the first event by the
probability of the second
event.
What you really need to know!
If the outcome of one
event does not affect
the outcome of a
second event, the
events are called
independent events.
What you really need to know!
If the outcome of one
event affects the outcome
of a second event, the
events are called
dependent events.
Link to Pre-Made Lesson
Example 1:
A number cube is rolled, and
the spinner shown is spun.
Find the probability of rolling a
2 and spinning a vowel.
1
1 2 2
1
P(2) 
 

6
6 5 30 15
2
P(vowel) 
5
Example 2:
A box contains 2 oatmeal, 3 strawberry, and
6 cinnamon snack bars. John reaches in
the box and randomly takes two snack bars,
one after the other. Find the probability that
he will choose a cinnamon bar and then a
strawberry bar.
6
P(C ) 
11
3
P( S ) 
10
6 3 18
9
 

11 10 110 55
Example 3:
Independent events
For lunch, Jessica may choose from
a turkey sandwich, a tuna
sandwich, a salad, or a soup. For a
drink, she can choose juice, milk, or
water. If she chooses a lunch at
random, what is the probability that
she chooses a sandwich (of either
kind) and juice?
The choice of sandwich has no
affect on how many drinks there are
to choose from.
2 1
P( sw)  
4 2
1
P( j ) 
3
1 1 1
P(sw and j)   
2 3 6
Example 4:
Dependent events
Mrs. Tierney will select two students
from her class to be on the
principal’s committee. She places
each name in a bag and selects
one at a time. The class contains
15 girls and 12 boys. What is the
probability she selects a girl’s name
first, then a boy’s name?
There will be one less possibility for the
second name after the first is selected.
15 5
P( g ) 

27 9
12 6
P(b) 

26 13
5 6 10
P(g then b)   
9 13 39
Page 399
Guided Practice
#’s 4-5
Read:
Pages 398-399
with someone at
home and study
examples!
Homework: Page 400-401
#’s 6-9, 11-19
#’s 25-32 all
Lesson Check Ch 9
Link to Lesson 9-7 Review Practice
Page
586
Lesson 9-7
Study Guide and Review
Pages
402-404
#’s 1-43
(Odd answers in back of book)
Prepare for Test!
Page
405
#’s 1-16
Lesson Check Ch 9
Prepare for Test!
Pages
406-407
#’s 1-17