1. Introduction to Probability
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Introduction to Probability
Course 1
Warm Up
Problem of the Day
Lesson Presentation

2. Introduction to Probability
Course 1
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Introduction to Probability
Warm Up
Write each fraction as a decimal and as a percent. 1. 2. 3. 4. 3 4 __
0.75; 75% 1 2 __
0.50; 50%
0.2; 22.2% __ 2 9 __ 3 8 __
0.375; 37.5%

3. Introduction to Probability
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Introduction to Probability
Problem of the Day
What fraction of the numbers from 0 to 99 are divisible by 3? or 34
100
___ 17 50 __

4. Introduction to Probability
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Introduction to Probability
Learn to estimate the likelihood of an event and to write and compare probabilities.

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Introduction to Probability
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Vocabulary
probability

6. Introduction to Probability
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Introduction to Probability
Probability is the measure of how likely an event is to occur.

7. Introduction to Probability
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Introduction to Probability
Probabilities are written as fractions or decimals from 0 to 1 or as percents from 0% to 100%. The higher an event’s probability, the more likely that event is to happen.
Events with a probability of 0, or 0%, never happen.
Events with a probability of 1, or 100%, always happen.
Events with a probability of 0.5, or 50%, have the same chance of happening as of not happening.

8. Introduction to Probability
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Introduction to Probability
Impossible Unlikely As likely as not Likely Certain 2 1 __
0% %
50%

9. Introduction to Probability Insert Lesson Title Here
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Introduction to Probability
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Additional Example 1: Estimating the Likelihood of an Event
Write impossible, unlikely, as likely as not, likely, or certain to describe each event.
A. You roll an even number on a standard number cube.
B. February has 28 days.
as likely as not
certain
A standard number cube is numbered from 1 to 6.
Helpful Hint

10. Introduction to Probability Insert Lesson Title Here
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Introduction to Probability
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Additional Example 1: Estimating the Likelihood of an Event
Write impossible, unlikely, as likely as not, likely, or certain to describe each event.
C. This spinner lands on blue.
D. This spinner lands on an odd number.
unlikely
impossible

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Introduction to Probability
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Check It Out: Example 1
Write impossible, unlikely, as likely as not, likely, or certain to describe each event.
A. You guess a number between 1 and 1,000.
B. You will roll an odd number on a standard number cube.
unlikely
as likely as not
A standard number cube is numbered from 1 to 6.
Helpful Hint

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Introduction to Probability
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Check It Out: Example 1
Write impossible, unlikely, as likely as not, likely, or certain to describe each event.
C. This spinner lands on green.
D. This spinner lands on an even number.
unlikely
certain

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Introduction to Probability
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Additional Example 2: Writing Probabilities
A. The weather report gives a 75% chance of snow. Write this probability as a decimal and as a fraction.
Write as a decimal.
75% = 0.75
Write as a fraction in simplest form.
75% = = 75
100
___ 3 4 __
B. The chance of being chosen is 0.8. Write this probability as a fraction and as a percent.
Write as a fraction in simplest form.
0.8 = = 8 10 __ 4 5
Write as a percent.
0.8 = 80%

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Introduction to Probability
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Additional Example 2: Writing Probabilities
C. There is a chance of getting a ring. Write
this probability as a decimal and as a percent. 7 50 __
= 7 ÷ 50 = 0.14 7 50 __
Write as a decimal.
= = = 14%
7 • 2
50 • 2
_____ 7 50 __ 14
100
___
Write as a percent.
In Example 2C, after you find the decimal form
of , you can use it to find the percent.
0.14 = 14%.
Helpful Hint 7 50 __

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Introduction to Probability
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Check It Out: Example 2
A. The weather report gives a 25% chance of snow. Write this probability as a decimal and as a fraction.
Write as a decimal.
25% = 0.25
Write as a fraction in simplest form.
25% = = 25
100
___ 1 4 __
B. The chance of being chosen is 0.6. Write this probability as a fraction and as a percent.
Write as a fraction in simplest form.
0.6 = = 6 10 __ 3 5
Write as a percent.
0.6 = 60%

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Introduction to Probability
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Check It Out: Example 2
C. There is a chance of getting a ring. Write
this probability as a decimal and as a percent. 4 25 __
= 4 ÷ 25 = 0.16 4 25 __
Write as a decimal.
= = = 16%
4 • 4
25 • 4
_____ 4 25 __ 16
100
___
Write as a percent.

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Introduction to Probability
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Additional Example 3A: Comparing Probabilities
On a standard number cube, there is a 50%
chance of rolling a multiple of 2 and a %
chance of rolling a multiple of 3. Is it more likely to roll a multiple of 2 or a multiple of 3? 1 3 __
Compare: % < 50% 1 3 __
It is more likely to roll a multiple of 2.

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Introduction to Probability
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Additional Example 3B: Comparing Probabilities
When you spin a certain spinner, there is a 15% chance that it will land on yellow, a 15% chance it will land on green, and a 70% chance that it will land on purple. Is it more likely to land on purple or on green?
Compare: 70% > 15%
It is more likely to land on purple than on green.

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Introduction to Probability
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Check It Out: Example 3A
When you spin a certain spinner, there is a 25% chance that it will land on purple, a 35% chance it will land on green, and a 40% chance that it will land on red. Is it more likely to land on red or on green?
Compare: 40% > 35%
It is more likely to land on red than on green.

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Introduction to Probability
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Check It Out: Example 3B
When you spin a certain spinner, there is a
9% chance that it will land on yellow, a %
chance it will land on brown, and a %
chance that it will land on blue. Is it more likely to land on brown or on yellow? 1 3 __ 2
Compare: 9% < % 1 3 __
It is more likely to land on brown than on yellow.

21. Introduction to Probability Insert Lesson Title Here
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Introduction to Probability
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Lesson Quiz
Write impossible, unlikely, as likely as not, likely, or certain to describe each event.
1. The sun will rise tomorrow.
2. You will roll 13 when rolling two dice.
3. There is a chance of picking the winning ticket. Write this probability as a fraction and as a percent.
4. At Hamburger Hut, there is a 20% chance of getting a plastic dinosaur cup and a 35% chance of getting a plastic rabbit cup. It is less likely that you will receive a rabbit cup or dinosaur cup?
certain
impossible
, 12.5% 1 8 __
dinosaur cup