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Logical Deduction - Aptitude Questions and Answers - RejinpaulPlacement

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In each of the questions below are given statements followed by four conclusions numbered I, II, III and IV, 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.

11.
Statements: All cups are glasses. Some glasses are bowls. No bowl is a plate.

Conclusions:
I.No cup is a plate.
II.No glass is a plate.
III.Some plates are bowls.
IV.Some cups are not glasses.
Answer & Solution
Answer: (A) None follows

Solution: All cups are glasses. Some glasses are bowls. Since the middle term 'glasses' is not distributed even once in the premises, no definite conclusion follows. Some glasses are bowls. No bowl is a plate. Since one premise is particular and the other negative, the conclusion must be particular negative and should not contain the middle term. So, it follows that 'Some glasses are not plates'.
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12.
Statements: Some bricks are trees. All trees are pens. All pens are boats.

Conclusions:
I.Some boats are bricks.
II.Some pens are bricks.
III.Some trees are bricks.
IV.Some bricks are boats.
Answer & Solution
Answer: (D) All follow

Solution: III is the converse of the first premise and so it holds. Some bricks are trees. All trees are pens. Since one premise is particular, the conclusion must be particular and should not contain the middle term. So, it follows that 'Some bricks are pens'. II is the converse of this conclusion and so it holds. All trees are pens. All pens are boats. Since both the premises are universal and affirmative, the conclusion must be universal affirmative and should not contain the middle term. So, it follows that 'All trees are boats'. Some bricks are trees. All trees are boats. Since one premise is particular, the conclusion must be particular and should not contain the middle term. So, it follows that 'Some bricks are boats'. Thus, IV follows. I is the converse of this conclusion and so it also holds.
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13.
Statements:Some dogs are rats. All rats are trees. Some trees are not dogs.

Conclusions:
I.Some trees are dogs.
II.All dogs are trees.
III.All rats are dogs.
IV.No tree is dog.
Answer & Solution
Answer: (B) Only I follows

Solution: Some dogs are rats. All rats are trees. Since one premise is particular, the conclusion must be particular and should not contain the middle term. So, it follows that 'Some dogs are trees'. I is the converse of this conclusion and so it holds. All rats are trees. Some trees are not dogs. Since the middle term 'trees' is not distributed even once in the premises, no definite conclusion follows.
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14.
Statements: All benches are desks. Some desks are roads. All roads are pillars.

Conclusions:
I.Some pillars are benches.
II.Some pillars are desks.
III.Some roads are benches.
IV.No pillar is bench.
Answer & Solution
Answer: (D) Only either I or IV, and II follow

Solution: All benches are desks. Some desks are roads. Since the middle term 'desks' is not distributed even once in the premises, no definite conclusion follows. Some desks are roads. All roads are pillars. Since one premise is particular, the conclusion must be particular and should not contain the middle term. So, it follows that 'Some desks are pillars'. II is the converse of this conclusion and so it holds. All benches are desks. Some desks are pillars. Since the middle term 'desks' is not distributed even once in the premises, no definite conclusion follows. However, I and IV involve the extreme terms and form a complementary pair. So, either I or IV follows.
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15.
Statements:Some taxis have horns. Some taxis have lights.

Conclusions:
I. Every taxi has either horn or light.
II.Some taxis have neither light nor horn.
III.Some taxis have horns as well as lights.
IV.No taxi has horn as well as light.
Answer & Solution
Answer: (D) Either III or IV follows

Solution: Since both the premises are particular, no definite conclusion follows. However, III and IV form a complementary pair. Thus, either III or IV follows.
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