1. Ratios, Rates and Percents
Lesson 16
Ratios, Rates and Percents
Introduction to Probability

2. Warm-Up Write each percent as a fraction in simplest form and a
decimal.
1. 35% %  
Write each fraction or decimal as a percent  
Jimmy bought a new television on sale for 30% off the original price. The original price was $1,200. How much was the discount on the television?

3. Introduction to Probability
Target:
Recognize probabilities that are unlikely and likely. Express probabilities as fractions, decimals and percents.

4. Vocabulary Probability: The measure of how likely it is something
will occur.

5. Example 1
Determine whether each event is impossible, unlikely, equally
likely, likely, or certain.
a. A card thrown on the floor lands face up.
Equally likely – only two options, no one is more likely than the other.
b. You roll a 2 on a regular number cube.
Unlikely – there are six numbers and 2 is only one of them.
c. You are older now than when you were born.
Certain – Everyone is older now than when they were born.

6. Example 2 Dexter’s teacher said there was an 80% chance of getting
math homework this weekend. Write this probability as a
simplified fraction and a decimal.
As a fraction:
As a decimal:
An 80% chance of math homework is the same as an 0.8 chance of homework or a chance of homework.

7. Example 3 Felipe asked 50 students Action: 40% of 50
which type of movie they
0.4 × 50 = 20 people
most preferred. Forty
Drama: of 50
percent chose action
movies, chose drama and
0.5 chose comedy. How
many of the students chose
Comedy: 0.5 of 50
each type of movie?
0.5 × 50 = 25 people

8. Exit Problems Determine whether each probability is impossible,
unlikely, equally likely, likely, or certain.
You roll a 1, 2, 3, 4 or 5 on a number cube.
You toss a coin and it lands “heads”.
You pick a blue sock out of a drawer filled with white and black socks.
There is a 0.6 chance that Tabitha will choose the winning card. Write this probability as a percent and a simplified fraction.

9. Communication Prompt
Decide whether you prefer to work with probabilities as percents, decimals, or simplified fractions. Why did you choose percents, decimals or simplified fractions? If you do not have a preference, explain why not.