Page 561 - Basic College Mathematics with Early Integers

538 C HAPTE R 7 I STATISTICS AND PROBABILITY

PRACTICE 3 Example 3 If a coin is tossed twice, find the probability of tossing heads on
If a coin is tossed three times, the first toss and then heads again on the second toss (H, H).
find the probability of tossing Solution: 1 way the event can occur
tails, then heads, then tails
T
(T, H, T). $%&
H, T, H, H, T, H, T, T
(''''')'''''*
4 possible outcomes
1 Number of ways the event can occur
probability =
4 Number of possible outcomes
1
The probability of tossing heads and then heads is .
4

Work Practice 3

PRACTICE 4 Example 4 If a die is rolled one time, find the probability of rolling a 3 or a 4.
If a die is rolled one time,
find the probability of rolling Solution: Recall that there are 6 possible outcomes when rolling a die.
a 2 or a 5.
2 ways that the event can occur
b R
possible outcomes: 1, 2, 3, 4, 5, 6
x
6 possible outcomes
2 Number of ways the event can occur
probability of a 3 or a 4 =
6 Number of possible outcomes
1
= Simplest form
3

Work Practice 4

11
Concept Check Suppose you have calculated a probability of . How do
9
you know that you have made an error in your calculation?

PRACTICE 5 Example 5 Find the probability of choosing a red marble from a box contain-
Use the diagram and informa- ing 1 red, 1 yellow, and 2 blue marbles.
tion in Example 5 and find the
probability of choosing a blue Solution: 1 way that event can occur
marble from the box. b

red yellow blue blue
(''''')'''''*
4 possible outcomes

Answers 1
probability =
1 1 1 4
3. 4. 5.
8 3 2 Copyright 2012 Pearson Education, Inc.
Work Practice 5
Concept Check Answer
The number of ways an event can occur
can’t be larger than the number of
possible outcomes.