Logical Deduction is reasoning which constructs or evaluates deductive arguments. Deductive arguments are attempts to show that a conclusion necessarily follows from a set of premises or hypotheses. A deductive argument is valid if the conclusion does follow necessarily from the premises, i.e., the conclusion must be true provided that the premises are true. A deductive argument is sound if it is valid and its premises are true. Deductive arguments are valid or invalid, sound or unsound. Deductive reasoning is a method of gaining knowledge.

Logical Reasoning

Logical Deductions-Exercise Questions

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Directions (1-2): In each question below are given two statements followed by two conclusions numbered I and II. You have to take the given two statements to be true even if they seem to be at variance from commonly known facts. Read the conclusion and then decide which of the given conclusions logically follows from the two given statements, disregarding commonly known facts.

Give answer:

(A) If only conclusion I follows

(B) If only conclusion II follows

(C) If either I or II follows

(D) If neither I nor II follows and

(E) If both I and II follow.

Statements: All tubes are handles. All cups are handles.

Conclusions:

1. All cups are tubes.

2. Some handles are not cups.

 

A) Only conclusion I follows

B) Only conclusion II follows

C) Either I or II follows

D) Neither I nor II follows

E) Both I and II follow

 

2.Statements: No magazine is cap. All caps are cameras.

Conclusions:

1.No camera is magazine.

2.Some cameras are magazines.

 

A)Only conclusion I follows

B)Only conclusion II follows

C)Either I or II follows

D)Neither I nor II follows

E)Both I and II follow

 

Direction (3-5) : In each of the questions below are given three statements followed by three conclusions numbered I, II and III, You have to take the given statements to be true even if they seem to be at variance from the commonly known facts. Read all the conclusions and then decide which of the given conclusions logically follows from the given statements disregarding commonly known facts.

 

3. Statements: Some pens are books. All schools are books. Some colleges are schools.

Conclusions:

  1. Some colleges are pens.
  2. Some pens are schools.
  3. Some colleges are books
  1. Only I and II follow
  2. Only II and III follow
  3. Only I and III follow
  4. All follow
  5. None of these

4. Statements: Some blades are hammers. Some hammers are knives. Some knives are axes.

Conclusions:

  1. Some axes are hammers.
  2. Some knives are blades.
  3. Some axes are blades.
    1. None follows
    2. Only I follows
    3. Only II follows
    4. Only III follows
    5. None of these

5. Statements: Some mountains are hillocks. Some mountains are rivers. Some mountains are valleys.

Conclusions:

  1. All mountains are either hillocks or rivers or valleys.
  2. No valley is river.
  3. Some river are valleys.
    1. None follows
    2. Only I follows
    3. Only either II or III follows
    4. Only III follows
    5. None of these

Answer & Explanations:

1. D. Both the premises are A type propositions. So, in either, the middle term 'handles' forming the predicate is not distributed. Since the middle term is not distributed even once in the premises, no definite conclusion follows.

2. C . As discussed above, the conclusion must be particular negative and should not contain the middle term. So, it follows that 'Some cameras are not magazines'. However, I and II involve only the extreme terms and form a complementary pair. Thus, either I or II follows.

3. E. Some pens are books. All schools are books.

Since the middle term 'books' is not distributed even once in the premises, so no definite conclusion follows.

Some colleges are schools. All schools are books.

Since one premise is particular, the conclusion must be particular and should not contain the middle term.

So, it follows that 'Some colleges are books'. Thus, III follows.

Some pens are books. Some colleges are books.

Since both the premises are particular, no definite conclusion can be drawn.

Hence, only III follows.

4. A . Since each combination of premises has two particular premises, so no definite conclusion follows.

5. C . Since each combination of premises shall contain two particular premises, no definite conclusion can be drawn. However, II and III are statements involving the extreme terms of the last two premises and form a complementary pair. Thus, either II or III follows.

Logical Deduction is reasoning which constructs or evaluates deductive arguments. Deductive arguments are attempts to show that a conclusion necessarily follows from a set of premises or hypotheses. A deductive argument is valid if the conclusion does follow necessarily from the premises, i.e., the conclusion must be true provided that the premises are true. A deductive argument is sound if it is valid and its premises are true. Deductive arguments are valid or invalid, sound or unsound. Deductive reasoning is a method of gaining knowledge. Freshersworld provides students or job seekers with questions and answers on logical deduction. It also provides Free Online Practice Tests, concepts, tricks and solved examples. What is difference between inductive and deductive reasoning? The inductive reasoning follows a particular flow or behaviour so as to make inferences, while deductive reasoning uses available information, facts or premises to arrive at a conclusion.
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