Logical Deduction - General Inteligence & Reasoning MCQ Questions and Answers

91

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.

A) Only I and II follow B) Only III and IV follow C) None follows D) All follow E) None of these

Discuss

Answer & Solution

Answer: Option D

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.

92

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.

A) None follows B) Only either I or III follows C) Only II and III follow D) Only III and IV follow

Discuss

Answer & Solution

Answer: Option A

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'.

93

Statements : Some trains are roads. No road is jungle. All flowers are jungles.

Conclusions:
I. Some trains are flowers.
II. Some trains are jungles.
III. Some flowers are trains.
IV. No road is flower.

A) None follows B) Only II follows C) Only III follows D) Only IV follows E) All follow

Discuss

Answer & Solution

Answer: Option D

Solution:

Some trains are roads. No road is jungle.

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 trains are not jungles'.

No road is jungle. All flowers are jungles.

Since both the premises are universal and one premise is negative, the conclusion must be universal negative and should not contain the middle term. So, it follows that 'No flower is road'. IV is the converse of this conclusion and so it holds.

Some trains are roads, No flower is road.

As discussed above, it follows that 'Some trains are not flowers'.

94

Statements : All doors are buses. All buses are leaves. No leaf is a flower.

Conclusions :
I. No flower is a door.
II. No flower is a bus.
III. Some leaves are doors.
IV. Some leaves are buses.

A) None follows B) Only I and II follow C) Only II and III follow D) Only II, III and IV follow E) All follow

Discuss

Answer & Solution

Answer: Option E

Solution:

IV is the converse of the second premise and so it holds.

All doors are buses. All buses are leaves.

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 doors are leaves'. III is the converse of this conclusion and so it holds.

All buses are leaves. No leaf is a flower.

Since both the premises are universal and one premise is negative, the conclusion must be universal negative and should not contain the middle term. So, it follows that 'No bus is flower'. II is the converse of this conclusion and so it holds.

All doors are buses. No bus is flower.

As discussed above, it follows that 'No door is flower'. I is the converse of this conclusion and so it also holds.

95

Statements : All oceans are rivers. Some springs are rivers. All wells are springs.

Conclusions :
I. Some springs are oceans.
II. Some wells are rivers.
III. Some rivers are oceans.
IV. No well is river.

A) None follows B) Only either I or III, and IV follow C) Only either II or IV, and III follow D) All follow E) Only either II or IV, and I follow

Discuss

Answer & Solution

Answer: Option C

Solution:

III is the converse of the first premise and so it holds.

All oceans are rivers. Some springs are rivers.

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

All wells are springs. Some springs are rivers.

Since the middle term 'springs' is not distributed even once in the premises, no definite conclusion follows. However, II and IV involve the extreme terms and form a complementary pair. Thus, either II or IV follows.

96

Statements : Some tigers are lions. Some lions are rabbits. Some rabbits are horses.

Conclusions :
I. Some tigers are horses.
II. Some rabbits are tigers.
III. Some horses are lions.
IV. All horses are rabbits.

A) All follow B) None follows C) Only I and II follow D) Only II and IV follow E) Only IV follows

Discuss

Answer & Solution

Answer: Option B

Solution:

Since each combination of premises shall contain two particular premises, no definite conclusion can be drawn.

97

Statements : Some spoons are bowls. All bowls are knives. All knives are forks.

Conclusions :
I. All spoons are forks.
II. All bowls are forks.
III. Some knives are bowls.
IV. Some forks are spoons.

A) Only II and III follow B) Only II and IV follow C) Only III and IV follow D) All follow E) None of these

Discuss

Answer & Solution

Answer: Option E

Solution:

III is the converse of the second premise and so it holds.

Some spoons are bowls. All bowls are knives.

Since one premise is particular, the conclusion must be particular and should not contain the middle term. So, it follows that 'Some spoons are knives'.

All bowls are knives. All knives are forks.

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 bowls are forks'. Thus, II follows.

Some spoons are knives. All knives are forks.

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

So, it follows that 'Some spoons are forks'. IV is the converse of this conclusion and so it follows.

Hence, II, III and IV follow.

98

Statements : All pencils are birds. All birds are skies. All skies are hills.

Conclusions :
I. All pencils are hills.
II. All hills are birds
III. All skies are pencils.
IV. All birds are hills.

A) Only I and II follow B) Only I and III follow C) Only III and IV follow D) All follow E) None of these

Discuss

Answer & Solution

Answer: Option E

Solution:

All pencils are birds. All birds are skies.

Since both the premises are universal and affirmative, the conclusion must be universal affirmative (A-type) and should not contain the middle term. So, it follows that 'All pencils are skies'.

All birds are skies. All skies are hills.

As discussed above, it follows that 'All birds are hills'. Thus, IV follows.

All pencils are skies. All skies are hills.

Clearly, it follows that 'All pencils are hills'. Thus, I follows. Hence, I and IV follow.

99

Statements : No tree is fruit. All fruits are stones. All stones are rains.

Conclusions :
I. No stone is tree.
II. No rain is tree.
III. Some rains are fruits.
IV. Some rains are trees.

A) Only either II or III, and I follow B) None follows C) Only either II or IV, and III follow D) All follow E) None of these

Discuss

Answer & Solution

Answer: Option C

Solution:

No tree is fruit. All fruits are stones.

Since the middle term 'fruits' is distributed twice, the conclusion must be particular.

Since one premise is negative, the conclusion must be negative. So, it follows that 'Some stones are not trees'.

All fruits are stones. All stones are rains. Clearly, it follows that 'All fruits are rains'. III is the converse of this conclusion and so it holds.

No tree is fruit, All fruits are rains. As discussed above, the conclusion must be particular negative and should not contain the middle term. So, it follows that 'Some rains are not trees'. However, II and IV involve only the extreme terms and form a complementary pair. Thus, either II or IV follows.

100

Statements : All players are spectators. Some spectators are theatres. Some theatres are dramas.

Conclusions :
I. Some dramas are spectators.
II. Some players are dramas.
III. Some theatres are players.
IV. All spectators are players.

A) None follows B) Only I and III follow C) Only II follows D) Only II and IV follow E) All follow

Discuss

Answer & Solution

Answer: Option A

Solution:

All players are spectators. Some spectators are theatres.

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

Some spectators are theatres. Some theatres are dramas.

Since both the premises are particular, no definite conclusion follows.