Page 165 - Math Course 1 (Book 2)

Probability of Simple Events

Mo. 11

Lesson 5 probability

Probability measures the chances of an event
happening. The probability of an event is a ratio
that compares the number of favorable outcomes
KEY CONCEPTS: to the number of possible outcomes.
1. Find the probability of simple events.
2. Use a sample to predict the actions of a
larger group. 0 1 4 or 0.25 1 2 or 0.50 3 4 or 0.75 1
3. Solving problems using experimental
probability of simple events
0% 25% 50% 75% 100%

impossible equally likely certain
MO. 11 - L5a to occur to occur to occur

Finding Probability of P (event) = number of favorable outcomes
Simple Events number of possible outcomes

sample space

Vocabulary A-Z The set of all possible outcomes is called the
sample space.
Let us learn some vocabulary

The sample space
outcomes for rolling 1 die is
the way things turn out; the results. {1, 2, 3, 4, 5, 6]

theoretical probability
What should occur in an experiment.
1
5 2

simple event Suppose a number cube is rolled. What is the
probability of rolling a prime number?
A simple event is one outcome or a collection of
outcomes. There are 3 prime numbers on a number cube: 2, 3
and 5.

There are 6 possible outcomes: 1, 2, 3, 4, 5 and 6.
number of favorable outcomes
Rolling a 6 on the die. P (event) =
number of possible outcomes

3 1 The probability of
= or rolling a prime
6 2 number is ½ or 50%.

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