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13.7 Probability

Models over a sample space, equally likely outcomes, unions and complements of events, and odds computed with permutations.

Algebra and Trigonometry 2e, 13.7 Probability

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87 exercises

Basic Probability. (Simple intro to sample spaces)

Tossing a coin:

  1. ⓐ Describe in set notation the sample space of tossing a coin.
  2. ⓑ Find the probability of “Coin lands on heads.”

Rolling a die:

  1. ⓐ Describe in set notation the event “Rolling an odd number.”
  2. ⓑ Find the probability of “Rolling an odd number.”

Drawing a card:

  1. ⓐ Describe in set notation the event “Drawing an Ace.”
  2. ⓑ Find the probability of “Drawing an Ace.”
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Constructing a Probability Model

Construct a probability model for rolling a single, fair die, with the event being the number shown on the die.

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13.7 Exercise 5

Construct a probability model for tossing a fair coin.

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Computing the Probability of an Event with Equally Likely Outcomes

A six-sided number cube is rolled. Find the probability of rolling an odd number.

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13.7 Exercise 7

A number cube is rolled. Find the probability of rolling a number greater than 2.

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Computing the Probability of the Union of Two Events

A card is drawn from a standard deck. Find the probability of drawing a heart or a 7.

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13.7 Exercise 9

A card is drawn from a standard deck. Find the probability of drawing a red card or an ace.

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Computing the Probability of the Union of Mutually Exclusive Events

A card is drawn from a standard deck. Find the probability of drawing a heart or a spade.

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13.7 Exercise 11

A card is drawn from a standard deck. Find the probability of drawing an ace or a king.

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Using the Complement Rule to Calculate Probabilities

Two six-sided number cubes are rolled.

  1. ⓐFind the probability that the sum of the numbers rolled is less than or equal to 3.
  2. ⓑFind the probability that the sum of the numbers rolled is greater than 3.
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13.7 Exercise 13

Two number cubes are rolled. Use the Complement Rule to find the probability that the sum is less than 10.

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Computing Probability Using Counting Theory

A child randomly selects 5 toys from a bin containing 3 bunnies, 5 dogs, and 6 bears.

  1. ⓐFind the probability that only bears are chosen.
  2. ⓑFind the probability that 2 bears and 3 dogs are chosen.
  3. ⓒFind the probability that at least 2 dogs are chosen.
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13.7 Exercise 15

A child randomly selects 3 gumballs from a container holding 4 purple gumballs, 8 yellow gumballs, and 2 green gumballs.

  1. ⓐFind the probability that all 3 gumballs selected are purple.
  2. ⓑFind the probability that no yellow gumballs are selected.
  3. ⓒFind the probability that at least 1 yellow gumball is selected.
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13.7 Exercise 16

What term is used to express the likelihood of an event occurring? Are there restrictions on its values? If so, what are they? If not, explain.

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13.7 Exercise 18

What is an experiment?

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13.7 Exercise 20

The union of two sets is defined as a set of elements that are present in at least one of the sets. How is this similar to the definition used for the union of two events from a probability model? How is it different?

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13.7 Exercise 22

Landing on a vowel

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13.7 Exercise 24

Landing on purple or a vowel

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13.7 Exercise 26

Landing on green or blue

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13.7 Exercise 28

Not landing on yellow or a consonant

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13.7 Exercise 30

Two coins are tossed.

Find the probability of tossing two heads.

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13.7 Exercise 32

Two coins are tossed.

Find the probability of tossing at least one tail.

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13.7 Exercise 34

Four coins are tossed.

Find the probability of tossing exactly two heads.

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13.7 Exercise 36

Four coins are tossed.

Find the probability of tossing four heads or four tails.

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13.7 Exercise 38

Four coins are tossed.

Find the probability of tossing not all tails.

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13.7 Exercise 40

Four coins are tossed.

Find the probability of tossing either two heads or three heads.

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13.7 Exercise 42

One card is drawn from a standard deck of 52 52 cards. Find the probability of drawing the following:

A two

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13.7 Exercise 44

One card is drawn from a standard deck of 52 52 cards. Find the probability of drawing the following:

Red six

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13.7 Exercise 46

One card is drawn from a standard deck of 52 52 cards. Find the probability of drawing the following:

A non-ace

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13.7 Exercise 48

Two dice are rolled, and the results are summed.

Construct a table showing the sample space of outcomes and sums.

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13.7 Exercise 50

Two dice are rolled, and the results are summed.

Find the probability of rolling at least one four or a sum of 8. 8.

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13.7 Exercise 52

Two dice are rolled, and the results are summed.

Find the probability of rolling a sum greater than or equal to 15. 15.

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13.7 Exercise 54

Two dice are rolled, and the results are summed.

Find the probability of rolling a sum less than 6 6 or greater than 9. 9.

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13.7 Exercise 56

Two dice are rolled, and the results are summed.

Find the probability of rolling a sum of 5 5 or 6. 6.

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13.7 Exercise 58

A coin is tossed, and a card is pulled from a standard deck. Find the probability of the following:

A head on the coin or a club

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13.7 Exercise 60

A coin is tossed, and a card is pulled from a standard deck. Find the probability of the following:

A head on the coin or a face card

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13.7 Exercise 62

Use this scenario: a bag of M&Ms contains 12 12 blue, 6 6 brown, 10 10 orange, 8 8 yellow, 8 8 red, and 4 4 green M&Ms. Reaching into the bag, a person grabs 5 M&Ms.

What is the probability of getting all blue M&Ms?

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13.7 Exercise 64

Use this scenario: a bag of M&Ms contains 12 12 blue, 6 6 brown, 10 10 orange, 8 8 yellow, 8 8 red, and 4 4 green M&Ms. Reaching into the bag, a person grabs 5 M&Ms.

What is the probability of getting 3 3 blue M&Ms?

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13.7 Exercise 66

Use the following scenario for the exercises that follow: In the game of Keno, a player starts by selecting 20 20 numbers from the numbers 1 1 to 80. 80. After the player makes his selections, 20 20 winning numbers are randomly selected from numbers 1 1 to 80. 80. A win occurs if the player has correctly selected 3,4, 3 , 4 , or 5 5 of the 20 20 winning numbers. (Round all answers to the nearest hundredth of a percent.)

What is the percen…

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13.7 Exercise 68

Use the following scenario for the exercises that follow: In the game of Keno, a player starts by selecting 20 20 numbers from the numbers 1 1 to 80. 80. After the player makes his selections, 20 20 winning numbers are randomly selected from numbers 1 1 to 80. 80. A win occurs if the player has correctly selected 3,4, 3 , 4 , or 5 5 of the 20 20 winning numbers. (Round all answers to the nearest hundredth of a percent.)

What is the percen…

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13.7 Exercise 70

Use the following scenario for the exercises that follow: In the game of Keno, a player starts by selecting 20 20 numbers from the numbers 1 1 to 80. 80. After the player makes his selections, 20 20 winning numbers are randomly selected from numbers 1 1 to 80. 80. A win occurs if the player has correctly selected 3,4, 3 , 4 , or 5 5 of the 20 20 winning numbers. (Round all answers to the nearest hundredth of a percent.)

How much less is…

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13.7 Exercise 72

Use this data for the exercises that follow: In 2013, there were roughly 317 million citizens in the United States, and about 40 million were elderly (aged 65 and over).United States Census Bureau. http://www.census.gov

If you meet five U.S. citizens, what is the percent chance that exactly one is elderly? (Round to the nearest tenth of a percent.)

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13.7 Exercise 74

Use this data for the exercises that follow: In 2013, there were roughly 317 million citizens in the United States, and about 40 million were elderly (aged 65 and over).United States Census Bureau. http://www.census.gov

If you meet five U.S. citizens, what is the percent chance that four are elderly? (Round to the nearest thousandth of a percent.)

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13.7 Exercise 76

Write the first four terms of the sequence defined by the recursive formula a 1 =2, a n = a n−1 +n. a_{1} = 2 , a_{n} = a_{n - 1} + n .

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13.7 Exercise 78

Write the first four terms of the sequence defined by the explicit formula a n = 10 n +3. a_{n} = 10^{n} + 3.

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13.7 Exercise 80

Is the sequence 4 7 , 47 21 , 82 21 , 39 7 ,... \frac{4}{7} , \frac{47}{21} , \frac{82}{21} , \frac{39}{7} , ... arithmetic? If so, find the common difference.

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13.7 Exercise 82

An arithmetic sequence has the first term a 1 =18 a_{1} = 18 and common difference d=−8. d = - 8. What are the first five terms?

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13.7 Exercise 84

Write a recursive formula for the arithmetic sequence −20,−10,0,10,… - 20 , - 10 , 0 , 10 ,\ldots

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13.7 Exercise 86

Write an explicit formula for the arithmetic sequence 7 8 , 29 24 , 37 24 , 15 8 ,… \frac{7}{8} , \frac{29}{24} , \frac{37}{24} , \frac{15}{8} , \ldots

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13.7 Exercise 88

Find the common ratio for the geometric sequence 2.5,5,10,20,… 2.5 , 5 , 10 , 20 , \ldots

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13.7 Exercise 90

A geometric sequence has terms a 7 =16,384 a_{7} = 16 , 384 and a 9 =262,144 a_{9} = 262 , 144. What are the first five terms?

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13.7 Exercise 92

What are the first five terms of the geometric sequence a 1 =3, a n =4⋅ a n−1 ? a_{1} = 3 , a_{n} = 4 \cdot a_{n - 1} ?

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13.7 Exercise 94

Write an explicit formula for the geometric sequence − 1 5 ,− 1 15 ,− 1 45 ,− 1 135 ,… - \frac{1}{5} , - \frac{1}{15} , - \frac{1}{45} , - \frac{1}{135} , \ldots

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13.7 Exercise 96

Use summation notation to write the sum of terms 1 2 m+5 \frac{1}{2} m + 5 from m=0 m = 0 to m=5. m = 5.

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13.7 Exercise 98

Use the formula for the sum of the first n n terms of an arithmetic series to find the sum of the first eleven terms of the arithmetic series 2.5, 4, 5.5, … .

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13.7 Exercise 100

Use the formula for the sum of the first n terms of a geometric series to find S 9 S_{9} for the series 12,6,3, 3 2 ,… 12 , 6 , 3 , \frac{3}{2} , \ldots

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13.7 Exercise 102

Find the sum of the infinite geometric series ∑ k=1 ∞ 45⋅ (− 1 3 ) k−1 . \sum_{k = 1}^{\infty} 45 \cdot \left(- \frac{1}{3}\right)^{k - 1} .

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13.7 Exercise 104

Alejandro deposits $80 of his monthly earnings into an annuity that earns 6.25% annual interest, compounded monthly. How much money will he have saved after 5 years?

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13.7 Exercise 106

How many ways are there to choose a number from the set {−10,−6, 4, 10, 12, 18, 24, 32} \left\{- 10 , - 6 ,\text{ } 4 ,\text{ } 10 ,\text{ } 12 ,\text{ } 18 ,\text{ } 24 ,\text{ } 32\right\} that is divisible by either 4 4 or 6? 6 ?

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13.7 Exercise 108

How many ways are there to construct a 4-digit code if numbers can be repeated?

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13.7 Exercise 110

Calculate P( 18,4 ). P \left(18 , 4\right) .

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13.7 Exercise 112

Calculate C( 15,6 ). C \left(15 , 6\right) .

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13.7 Exercise 114

How many subsets does the set { 1,3,5,…,99 } \left\{1 , 3 , 5 , \ldots , 99\right\} have?

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13.7 Exercise 116

How many distinct ways can the word DEADWOOD be arranged?

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13.7 Exercise 118

Evaluate the binomial coefficient ( 23 8 ). \begin{pmatrix} 23 \\ 8 \end{pmatrix} .

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13.7 Exercise 120

Use the Binomial Theorem to write the first three terms of ( 2a+b ) 17 . \left(2 a + b\right)^{17} .

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13.7 Exercise 122

Assume two die are rolled.

Construct a table showing the sample space.

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13.7 Exercise 124

Assume two die are rolled.

What is the probability of rolling a pair?

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13.7 Exercise 126

Assume two die are rolled.

What is the probability that a roll doesn’t include a 2 or result in a pair?

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13.7 Exercise 128

Assume two die are rolled.

What is the probability that a roll includes neither a 5 nor a 6?

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13.7 Exercise 130

Use the following data: An elementary school survey found that 350 of the 500 students preferred soda to milk. Suppose 8 children from the school are attending a birthday party. (Show calculations and round to the nearest tenth of a percent.)

What is the percent chance that at least one of the children attending the party prefers milk?

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13.7 Exercise 132

Use the following data: An elementary school survey found that 350 of the 500 students preferred soda to milk. Suppose 8 children from the school are attending a birthday party. (Show calculations and round to the nearest tenth of a percent.)

What is the percent chance that exactly 3 of the children attending the party prefer milk?

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13.7 Exercise 133

Write the first four terms of the sequence defined by the recursive formula a=–14, a n = 2+ a n–1 2 . a = – 14 , a_{n} = \frac{2 + a_{n – 1}}{2} .

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13.7 Exercise 135

Is the sequence 0.3,1.2,2.1,3,… 0.3 , 1.2 , 2.1 , 3 , \ldots arithmetic? If so find the common difference.

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13.7 Exercise 137

Write a recursive formula for the arithmetic sequence −2,− 7 2 ,−5,− 13 2 ,… - 2 , - \frac{7}{2} , - 5 , - \frac{13}{2} , \ldots and then find the 22nd term.

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13.7 Exercise 139

Is the sequence −2,−1,− 1 2 ,− 1 4 ,… - 2 , - 1 , - \frac{1}{2} , - \frac{1}{4} , \ldots geometric? If so find the common ratio. If not, explain why.

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13.7 Exercise 141

Write a recursive formula for the geometric sequence 1,− 1 2 , 1 4 ,− 1 8 ,… 1 , - \frac{1}{2} , \frac{1}{4} , - \frac{1}{8} , \ldots

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13.7 Exercise 143

Use summation notation to write the sum of terms 3 k 2 − 5 6 k 3 k^{2} - \frac{5}{6} k from k=−3 k = - 3 to k=15. k = 15.

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13.7 Exercise 145

Use the formula for the sum of the first n n terms of a geometric series to find ∑ k=1 7 −0.2⋅ ( −5 ) k−1 . \sum_{k = 1}^{7} - 0.2 \cdot \left(- 5\right)^{k - 1} .

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13.7 Exercise 147

Ramla deposits $3,600 into a retirement fund each year. The fund earns 7.5% annual interest, compounded monthly. If she opened her account when she was 20 years old, how much will she have by the time she’s 55? How much of that amount was interest earned?

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13.7 Exercise 149

A buyer of a new sedan can custom order the car by choosing from 5 different exterior colors, 3 different interior colors, 2 sound systems, 3 motor designs, and either manual or automatic transmission. How many choices does the buyer have?

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13.7 Exercise 151

A music group needs to choose 3 songs to play at the annual Battle of the Bands. How many ways can they choose their set if they have 15 songs to pick from?

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13.7 Exercise 153

How many distinct ways can the word EVANESCENCE be arranged if the anagram must end with the letter E?

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13.7 Exercise 155

Find the seventh term of ( x 2 − 1 2 ) 13 \left(x^{2} - \frac{1}{2}\right)^{13} without fully expanding the binomial.

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13.7 Exercise 157

What is the probability of landing on an odd number?

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13.7 Exercise 159

What is the probability of landing on blue or an odd number?

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13.7 Exercise 161

A bowl of candy holds 16 peppermint, 14 butterscotch, and 10 strawberry flavored candies. Suppose a person grabs a handful of 7 candies. What is the percent chance that exactly 3 are butterscotch? (Show calculations and round to the nearest tenth of a percent.)

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Adapted from College Algebra © 2021 Rice University. Licensed under CC BY 4.0. Sources: College Algebra 2e, Algebra and Trigonometry 2e, Precalculus 2e, College Algebra with Corequisite Support 2e. Imported at revision 4922e46.