Lesson 9-2 Pages 374-377

Tree Diagrams

Lesson Check 9-1

What you will learn!

How to use tree diagrams to count outcomes and

find probabilities.

Fair gameFair gameTree diagramTree diagramSample spaceSample space

What you really need to know!

A game in which players of equal skill have an equal chance of winning is a fair game. A tree diagram is used to show all of the possible outcomes, or sample space, in a probability experiment.

Link to Pre-Made Lesson

Example 1:

Tom flips two coins. Draw a tree diagram to show the sample space of how the coins can land. Then determine the probability of flipping two tails.

First First CoinCoin

H

T

H

T

T

H

HH

HT

TH

TT

Second Second CoinCoin

Sample Sample SpaceSpace

The probability of flipping two tails is:

possible

favorableP(tails)

4

1

Choices x Choices = Number of outcomes

2 x 2 = 4 possibilities

Example 1: Method 2

4

1

possible

favorableP(tails)

Example 2:

An ice cream sundae at the Ice Cream Shoppe is made from one flavor of ice cream and one topping. For ice cream flavors, you can choose from chocolate, vanilla, and strawberry.

Example 2:

For toppings you can have hot fudge, butterscotch, or marshmallow. Find the number of different sundaes that are possible.

Ice CreamIce Cream

9 possibilities!C

V

S

F

B

M

F

B

M

F

B

M SM

CF

CB

CM

VF

VB

VMSF

SB

ToppingTopping Sample SpaceSample Space

Choices x Choices = Number of outcomes

3 x 3 = 9 possibilities

Example 2: Method 2

Example 3:

If you are given a sundae at random from the shop in the previous problem, what is the probability that it has vanilla ice cream?

Ice CreamIce Cream ToppingTopping Sample SpaceSample Space

9 possibilities!C

V

S

F

B

M

F

B

M

F

B

M SM

CF

CB

CM

VF

VB

VMSF

SB

Example 3:

If you are given a sundae at random from the shop in the previous problem, what is the probability that it has vanilla ice cream?

possible

favorableP(vanilla)

3

1

9

3

Page 376

Guided Practice

#’s 3-6

Pages 374-375 with someone at home and study

examples!

Read:

Homework: Page 376-377

#’s 7-19 all

#’s 23-33

Lesson Check 9-2THQ 9-1/9-2 Tree Diagrams

Page

585

Lesson 9-2

Lesson Check 9-2

Example 1:

A family has two children. Draw a tree diagram to show the sample space of the children’s genders. Then determine the probability of the family having two girls.

First First ChildChild

Second Second ChildChild

Sample Sample SpaceSpace

B

G

B

G

BB

BG

GB

GG

B

G

The probability of having two girls is:

possible

favorableP(girls)

4

1

THQ 9-1 to 9-2

Tree Diagrams

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# 4

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