Page 219 - Algebra 1

L E S S O N Finding the Probability of Independent and
Dependent Events
33
Warm Up
1. Vocabulary A is the set of all possible outcomes of
New Concepts
(14)
an event.
A number cube is labeled 1-6. Suppose the number cube is rolled once. (14)
2. List all the possible outcomes.
3. What is the probability of rolling a prime number?
Simplify.
4. _4 · _15 5. _18(-_33)
(11) 5 22 (11) 55 54
Events where the outcome of one does not affect the probability of the other are called independent events. To find the probability of two independent events, multiply the probabilities of the two events.
12
53 4
Spinning a spinner and flipping a coin are independent events. The result of one does not affect the result of the other. What is the probability of spinning a 3 and landing on heads?
P(3 and heads) = P(3) · P(heads) = _1 · _1
52
= _1 10
Spinning the spinner twice also creates two independent events. The first spin does not affect the second spin. What is the probability of spinning a 5 and then a 1?
P(5 and 1) = P(5) · P(1) = _1 · _1
55
= _1 25
With dependent events, the outcome of one event does affect the probability of the other event. To find the probability of two dependent events, you multiply the probability of the first event by the probability of the second event, given the results of the first event.
Math Reasoning
Write Explain why the first spin does not affect the second spin.
Online Connection www.SaxonMathResources.com
204 Saxon Algebra 1