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Objective

Find the probability of a simple event

Vocabulary

Outcome

One possible result of a probability event

Vocabulary

Simple event

One outcome or a collection of outcomes

Vocabulary

Probability

The chance that some event will happen.

A ratio

Ways an event can occurNumber of Possible Outcomes

Vocabulary

Random

Outcomes occur at random if each outcome is equally likely to occur

Vocabulary

Complementary event

The events of one outcome happening and that outcome not happening are complementary

events.

The sum of the probabilities of complementary events is 1

Example 1 Find Probability

Example 2 Find Probability

Example 3 Find a Complementary Event

If the spinner is spun once, what is the probability of it landing on an odd number?

1/3

Write probability statement

Numerator is “odd numbers possible”

Denominator is “total numbers possible”

odd number

If the spinner is spun once, what is the probability of it landing on an odd number?

1/3

Count how many “odd numbers”

1 and 3 are odd numbers

Place 2 in the numerator

If the spinner is spun once, what is the probability of it landing on an odd number?

1/3

Count how many “total numbers” are on the spinner

There are 4 numbers on the spinner

Place 4 in the denominator

If the spinner is spun once, what is the probability of it landing on an odd number?

1/3

Find the GCF = 2

Divide GCF into numerator and denominator

2 2

Answer:

What is the probability of rolling a number less than three on a number cube marked with 1, 2, 3, 4, 5, and 6 on its faces?

Answer: P (number less than 3) =

1/3

NOTE: A number cube is a number dice

The bookstore at the mall has 15 math books, 20 science books, 10 literature books and 5 history books for a give-away promotion. The clerk will select a book at random to give to each customer. What is the probability that the clerk will select a literature book?

2/3

Write probability statement

probability literature book

P (literature book) =

Numerator will be “number of literature books”

number of literature books

Denominator will be “total number of books”

total number of books

The bookstore at the mall has 15 math books, 20 science books, 10 literature books and 5 history books for a give-away promotion. The clerk will select a book at random to give to each customer. What is the probability that the clerk will select a literature book?

2/3

Replace literature books with 10

probability literature book

P (literature book) = number of literature bookstotal number of books

P (literature book) = 10

Count total number of books

15 + 20 + 10 + 5 = 50

50

The bookstore at the mall has 15 math books, 20 science books, 10 literature books and 5 history books for a give-away promotion. The clerk will select a book at random to give to each customer. What is the probability that the clerk will select a literature book?

2/3

probability literature book

P (literature book) = number of literature bookstotal number of books

P (literature book) = 1050

Find the GCF = 10

Divide GCF into numerator and denominator

10 10

P (literature book) = 1 5

Answer:

GAMES A game requires rolling a number cube marked with 1, 2, 3, 4, 5, and 6 on its. If the roll is four or less, the player wins. What is the probability of winning the game?

Answer: P (4 or less) =

2/3

2 3

GAMES A game requires spinning the spinner. If the spin is 6 or greater, the player wins. What is the probability of not winning the game?

P (5 or less) =

3/3

Write probability statement

probability of not winning

To win, must have 6 or greater

So to lose, must have 5 or less

GAMES A game requires spinning the spinner. If the spin is 6 or greater, the player wins. What is the probability of not winning the game?

P (5 or less) =

3/3

Numerator is “numbers 5 or less”

probability of not winning

numbers 5 or less

Denominator is “total number of numbers”

total number of numbers

GAMES A game requires spinning the spinner. If the spin is 6 or greater, the player wins. What is the probability of not winning the game?

P (5 or less) =

3/3

probability of not winning

numbers 5 or less total number of numbers

Count numbers that are 5 or less

P (5 or less) = 5

Count all the numbers

8

GAMES A game requires spinning the spinner. If the spin is 6 or greater, the player wins. What is the probability of not winning the game?

P (5 or less) =

3/3

probability of not winning

numbers 5 or less total number of numbers

P (5 or less) = 5 8 Find the GCF = 1

Answer:

NOTE: This is a complementary event

GAMES A game requires rolling a number cube marked with 1, 2, 3, 4, 5, and 6 on its faces. If the roll is two or less, the player wins. What is the probability of not winning the game?

Answer:

*

P (not winning) =

3/3

2 3

NOTE: This is a complementary event

Assignment Lesson 9:1 Simple Events 10 - 26 All