Logical Deduction - Section 1
Practice and master this topic with our carefully crafted questions.
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 men are dogs. All dogs are cats.
Conclusions:
I. All men are cats.
II. All cats are men.
Since both the premises are universal and affirmative, the conclusion must be universal affirmative. However, conclusion II, being an A-type proposition, distributes the term 'cats'.
Since the term 'cats' is distributed in II without being distributed in any of the premises, so conclusion II cannot follow. Thus, only I follows.
Statements: All tubes are handles. All cups are handles.
Conclusions:
I. All cups are tubes.
II. Some handles are not cups.
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
Statements: No magazine is cap. All caps are cameras.
Conclusions:
I. No camera is magazine.
II. Some cameras are magazines.
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.
Statements: All huts are mansions. All mansions are temples.
Conclusions:
I. Some temples are huts.
II. Some temples are mansions.
As discussed above, it follows that 'All huts are temples'. I is the converse of this conclusion and so it holds. II is the converse of the second premise and so it also holds.
Statements: Some books are tables. Some tables are mirrors.
Conclusions:
I. Some mirrors are books.
II. No book is mirror.
Since both the premises are particular no definite conclusion follows. However, I and II involve only the extreme terms and form a complementary pair. Thus, either I or II follows.
Statements: All trucks fly. Some scooters fly.
Conclusions:
I. All trucks are scooters.
II. Some scooters do not fly.
Since the middle term 'fly' is not distributed even once in the premises, no definite conclusion follows.
Statements: All windows are doors. No door is wall.
Conclusions:
I. No window is wall.
II. No wall is door.
Since both the premises are universal and one premise is negative, the conclusion must be universal negative. Also, the conclusion should not contain the middle term. So, I follows. However, II is the converse of the second premise and thus it also holds.
Conclusions:
I. Some students are boys.
II. Some teachers are students.
Since both the premises are particular, no definite conclusion follows. However, I is the converse of the second premise and thus it holds.
Statements: No man is a donkey. Rahul is a man.
Conclusions:
I. Rahul is not a donkey.
II. All men are not Rahul.
Since on premise is negative, the conclusion must be negative. Conclusion II cannot follow as it contains the middle term. So, only I follows.
Statements: Some books are pens. No pen is pencil.
Conclusions:
I. Some books are pencils.
II. No book is pencil.
As discussed above, the conclusion must be particular negative and should not contain the middle term. So, it follows that 'Some books are not pencils'. However, I and II involve only the extreme terms and form a complementary pair. Thus, either I or II follows.