1. An Introduction To Probability
Algebra 2

2. Definitions:
Probability: the likelihood that an event will occur. Has to be a number between 0 and 1.
An event that is certain to occur has a probability of 1
An event that cannot occur has a probability of 0
An event that is equal likely and unlikely has a probability of ½ .

3. The Theoretical Probability Of An Event
When all outcomes are equally likely the theoretical probability that an even A will occur is…
Theoretical Probability is often just called probability

4. Probability
Probability can be expressed as either a fraction, decimal, or percent.

5. Example:
A spinner has 8 equal-size sectors numbered from 1 to 8. Find the probability of
Spinning a 6.
Spinning a number greater than 5.

6. Example:
There are 9 students on the math team. You draw their names one by one to determine the order in which they answer questions at a math meet. What is the probability that 3 of the five seniors on the team will be chosen last, in any order.

7. Example:
Five cards are drawn from a standard 52-card deck. What is the probability that the first 2 cards are red.

8. Experimental Probability
Experimental Probability: A calculation of the probability of an event based on performing an experiment, conducting a survey, or looking at the history of an event.

9. Example:
Ninth graders must enroll in one math class. The enrollments of ninth grade student the previous year are shown in the bar graph. Find the probability that a randomly chosen student from this year’s ninth grade class is enrolled in
Consumer Math
Algebra 1 or Introduction to Algebra

10. Example:
You made 15 of 21 free throw attempts. Find the probability that you will make you next free throw.

11. Geometric Probabilities
Geometric Probability: probabilities found by calculating a ratio of two lengths, areas, or volumes

12. Example:
Find the probability that a randomly thrown dart would hit the shaded portion of the target.

13. Example:
A store is open from 8am to 8pm. The manager works from 9am to 4pm. What is the probability that the manager is there during the same time as a customer who arrives randomly during the store’s hours of operation and stays for 15 minutes?

14. Example:
The target for a bean bag toss game is a rectangle 3 feet wide and 4 feet with 3 circular holes each with a radius of 1 foot. What is he probability that a bean bag thrown randomly at the target will pass through one of the holes.