Solved Examples on Propositional Logic

Samuel Dominic Chukwuemeka (SamDom For Peace)
Solve all questions.
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You may use any of the Laws of Logical Equivalences and/or Logical Equivalences for Propositional Logic and Predicate Logic.
For any law of logical equivalence that you use, please indicate the law or the logical equivalence number.

(1.) Decide whether these statements makes sense​ (or is clearly​ true) or does not make sense​ (or is clearly​ false).
Explain your reasoning.

(a.) My logical proposition is a question that you must answer.

(b.) The United States intends to capture​ the terrorist, dead or alive.

(c.) When Sally is​ depressed, she listens to music. I saw her today listening to​ music, so she must have been depressed.

(d.) Now that​ I've studied​ logic, I can always determine the truth of any statement by making a truth table for it.

(e.) If all novels are​ books, then all books are novels.


(a.) Propositions are not questions. So, the statement does not make sense.

(b.) The statement makes sense because when the terrorist the statement is referring to is​ caught, he must be either dead or alive.

(c.) The statement does not make sense.
Sally listens to music when she is​ depressed, but the statement does not clearly state that this is the only time Sally listens to music.

(d.) The statement does not make sense.
A truth table displays each possible set of truth values for the propostions being​ considered, but does not always make a definitive conclusion about the propostion.

(e.) The statement does not make sense.
Not all books are novels.
(2.) Which of the following is an:
(I.) Inclusive Disjunction
(II.) Exclusive Disjunction

A. An integer is either a positive number or a negative number.
B. Two lines are parallel or intersect at a point.
C. A​ non-zero number can be greater than or less than zero.
D. A quadrilateral can be a polygon with 4 sides or a polygon with 4 vertices.
E. Someone will read a book or a magazine the next time I go to the library.
F. The insurance covers a trip to the​ doctor's office or a trip to the emergency room.
G. The rules clearly state that chewing gum or eating food is not permitted.
H. Before the​ test, someone have the choice of studying or watching television.
I. Her favorite sport is tennis or golf.
J. He will eat supper at restaurant A or restaurant B.
K. For elective classes, she could take Spanish or Arabic.


Let us analyze each option: (based on the possibilities of only what we are given rather than all possibilities)

A. An integer is either a positive number or a negative number.
An integer cannot be both a positive number and a negative number.
Based on what we are given: this is an Exclusive OR
Based on all possibilities:
An integer can also be zero. Zero is neither a positive number nor a negative number.

B. Two lines are parallel or intersect at a point.
Based on what are given: this is an Exclusive OR because two lines will either not meet (parallel) or meet(intersect) at a point.
Two lines cannot meet, and meet at a point.

C. A​ non-zero number can be greater than or less than zero.
This is an Exclusive OR
A non-zero number is either greater than zero or less than zero. It cannot be both.

D. A quadrilateral can be a polygon with 4 sides or a polygon with 4 vertices.
Examples of quadrilaterals are: square, rectangle, rhombus, kite, parallelogram, trapezium
These are polygons with four sides and four vertices.
They have four sides.
They have four vertices.
They have four sides and four vertices.
This is an example of Inclusive OR

E. I will read a book or a magazine the next time I go to the library.
Technically speaking, magazine is a book. Be it as it may, one can read a book and a magazine at the same time.
One can read a book.
One can read a magazine.
One can read a book and a magazine simultaneously.
This is an example of Inclusive OR

F. My insurance covers a trip to the​ doctor's office or a trip to the emergency room.
The insurance can cover a trip to the doctor's office.
The insurance can also cover a trip to the emergency room.
The insurance can conver a trip to the doctor's office and a trip to the emergency room.
This is an example of Inclusive OR

The rules clearly state that chewing gum or eating food is not permitted.
This implies that chewing gum is not permitted.
Eating food is not permitted.
Chewing gum and eating food is not permitted.
This is an example of Inclusive OR

H. Before the​ test, someone have the choice of studying or watching television.
Someone can be studying.
Someone can be watching television.
However, someone cannot be studying and watching television simultaneously.
This is an example of Exclusive OR

I. Her favorite sport is tennis or golf.
Her favorite sport [emphasis on sport (not sports)] cannot be both tennis and golf. It has to be just one of them.
This is an example of Exclusive OR

J. He will eat supper at restaurant A or restaurant B.
He cannot eat supper at the two restaurants simultaneously. He will either eat at restaurant A or restaurant B but not both.
This is an example of Exclusive OR

K. For elective classes, she could take Spanish or Arabic.
She could take Spanish.
She could take Arabic.
She could take both Spanish and Arabic.
This is an example of Inclusive OR

(3.) Explain the meaning of each given​ statement, which contains a mulitple negation.
Then answer the question that follows.
Sarah did not decline the offer to go to dinner.
Did Sarah go to​ dinner?

A. The first negation​ "decline the​ offer" makes it seem that Sarah would not go to dinner.
But the statement negates this​ negation, "did not decline the​ offer."
Therefore, Sarah accepts the offer to go to dinner.

B. The first negation​ "decline the​ offer" makes it seem that Sarah would go to dinner.
But the statement negates this​ negation, "did not decline the​ offer."
Therefore, Sarah declines the offer to go to dinner.

C. The first negation​ "decline the​ offer" makes it seem that Sarah would go to dinner.
The statement reinforces this negation, "did not decline the​ offer."
Therefore, Sarah accepts the offer to go to dinner.

D. The first negation​ "decline the​ offer" makes it seem that Sarah would not go to dinner.
The statement reinforces this​ negation, "did not decline the​ offer."
Therefore, Sarah declines the offer to go to dinner.


A. The first negation​ "decline the​ offer" makes it seem that Sarah would not go to dinner.
But the statement negates this​ negation, "did not decline the​ offer."
Therefore, Sarah accepts the offer to go to dinner.
(4.) Determine if each of the following statements is a​ proposition, and give an explanation.

(a.) Some women have served as United States Senators.

(b.) Turn off the lights.

(c.) Who cares?


(a.) Yes, because the given statement can be either true or​ false, and it is a complete sentence.

(b.) No, because the statement does not make a​ claim, and it is not a complete sentence.

(c.) No, because the statement does not make a​ claim; it is a question.
(5.) Rephrase the following statements using one or more conditional statements​ (if p, then​ q).

(a.) Without adversity​, you​ don't have triumph. Without ​triumph, you have nothing.

(b.) Even if​ you're flipping burgers at a carnival​, if you are great​, everybody wants to be in your line.

(c.) Whenever the student attends his class, the student acquires new knowledge.

(d.) Not winning is a sufficient condition for losing.

(a.) If you​ don't have adversity​, then you​ don't have triumph. If you​ don't have triumph​, then you have nothing.

(b.) If you are great at flipping burgers at a carnival​, then everyone will want to be in your line.

(c.) If the student attends his class, the student acquires new knowledge.

(d.) If someone is not winning, then the person is losing.
(6.) Write the negation of these propositions.
Then state the truth value of the original proposition and its negation.

(a.) Spain is in South America.

(b.) October does not come before September.


(a.) $p$ Spain is in South America.
Truth value is: F
$\neg p$: Spain is not in South America.
Truth value is: T

(b.) $p$: October does not come before September.
Truth value is T
$\neg p$: October does comes before September.
Truth value is F

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(10.) Explain the meaning of each given​ statement, which contains a mulitple negation.
Then answer the question that follows.
The mayor opposes the ban on​ anti-fracking rallies.
Does the mayor approve of allowing the​ rallies?

A. The mayor believes that​ anti-fracking is the best reason to rally.
So, the mayor approves of allowing the rallies.

B. The mayor believes that​ anti-fracking is not a valid reason to rally.​
So, the mayor does not approve of allowing the rallies.

C. The mayor believes that a ban on​ anti-fracking rallies should not be allowed.​
So, the mayor approves of allowing the rallies.

D. The mayor believes that a ban on​ anti-fracking rallies should be allowed.
So, the mayor does not approve of allowing the rallies.


C. The mayor believes that a ban on​ anti-fracking rallies should not be allowed.​
So, the mayor approves of allowing the rallies.
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(13.) Explain the meaning of each given​ statement, which contains a mulitple negation.
Then answer the question that follows.
Did the Congressman vote in favor of​ discrimination?
The Congressman voted against the​ anti-discrimination bill.

A. The statement means that the Congressman did not vote in favor of a bill that favors discrimination.​
So, the Congressman voted in favor of discrimination.

B. The statement means that the Congressman did not vote in favor of a bill that does not favor discrimination.​
So, the Congressman voted against discrimination.

C. The statement means that the Congressman did not vote in favor of a bill that does not favor discrimination.​
So, the Congressman voted in favor of discrimination.

D. The statement means that the Congressman voted in favor of a bill that does not favor discrimination.​
So, the Congressman voted against discrimination.


C. The statement means that the Congressman did not vote in favor of a bill that does not favor discrimination.​
So, the Congressman voted in favor of discrimination.
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(18.) Explain the meaning of each given​ statement, which contains a mulitple negation.
Then answer the question that follows.
The house failed to overturn the veto on a bill that would stop logging.
Based on this​ vote, will logging​ continue?

A. The house voted to overturn the veto.
This outcome will allow logging to continue.

B. The house voted not to overturn the veto.
This outcome will allow logging to continue.

C. The house voted not to overturn the veto.
This outcome will not allow logging to continue.

D. The house voted to overturn the veto.
This outcome will not allow logging to continue.


B. The house voted not to overturn the veto.
This outcome will allow logging to continue.
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(24.) Explain the meaning of each given​ statement, which contains a mulitple negation.
Then answer the question that follows.
The senator opposes overriding the​ governor's veto of the bill.
Does the senator support the​ bill?

A. The senator opposes the​ governor's stance on the​ bill, so the senator does support the bill.

B. The senator opposes the​ governor's stance on the​ bill, so the senator does not support the bill.

C. The senator supports the​ governor's stance on the​ bill, so the senator does support the bill.

D. The senator supports the​ governor's stance on the​ bill, so the senator does not support the bill.


D. The senator supports the​ governor's stance on the​ bill, so the senator does not support the bill.
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(27.) Explain the meaning of each given​ statement, which contains a mulitple negation.
Then answer the question that follows.
Paul denies that he opposes the plan to build a new dorm.
Does Paul support building a new​ dorm?

A. The first negation​ "opposes the​ plan" makes it seem that Paul would not support the new dorm.
But the statement negates this​ negation, "Paul denies that he opposes the​ plan."
Therefore, it seems that Paul supports the plan for the new dorm.

B. The first negation​ "opposes the​ plan" makes it seem that Paul supports the new dorm.
But the statement negates this​ negation, "Paul denies that he opposes the​ plan."
Therefore, it seems that Paul opposes the plan for the new dorm.

C. The first negation​ "opposes the​ plan" makes it seem that Paul supports the new dorm.
The statement reinforces this​ negation, "Paul denies that he opposes the​ plan."
Therefore, it seems that Paul supports the plan for the new dorm.

D. The first negation​ "opposes the​ plan" makes it seem that Paul would not support the new dorm.
The statement reinforces this​ negation, "Paul denies that he opposes the​ plan."
Therefore, it seems that Paul opposes the plan for the new dorm.


A. The first negation​ "opposes the​ plan" makes it seem that Paul would not support the new dorm.
But the statement negates this​ negation, "Paul denies that he opposes the​ plan."
Therefore, it seems that Paul supports the plan for the new dorm.
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