Logical Deduction - Section 4 (1)
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In each of the following questions, three statements are given followed by four conclusions numbered I, II, III and TV. You have to take the given statements to be true even if they seem to be at variance with commonly known facts and then decide which of the given conclusions logically follows from the given statements disregarding commonly known facts.
| 1. | Statements: All jungles are buses. All books are buses. All fruits are books. Conclusions: Some fruits are jungles. Some buses are books. Some buses are jungles. All fruits are buses. |
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Answer: Option C Explanation: III is the converse of the first premise and II is the converse of the second premise. So, both of them hold. All fruits are books. All books are buses. 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 fruits are buses'. Thus, IV follows. All jungles are buses. All books are buses. Since the middle term 'buses' is not distributed ever once in the premises, no definite conclusion follows. All fruits are buses. All books are buses. As discussed above, no definite conclusion can be drawn. All jungles are buses. All fruits are buses. Again, no definite conclusion follows. |
| 2. | Statements: No table is fruit. No fruit is window. All windows are chairs. Conclusions: No window is table. No chair is fruit. No chair is table. All chairs are windows. |
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Answer: Option A Explanation: No table is fruit. No fruit is window. Since both the premises are negative, no definite conclusion follows. No fruit is window. All windows are chairs. Since the middle term 'windows' is distributed twice and one premise is negative, the conclusion must be particular negative. So, it follows that 'Some chairs are not fruits'. |
| 3. | Statements: Some tapes are discs. Some discs are cassettes. Some cassettes are songs. Conclusions: Some songs are discs. Some cassettes are tapes. Some songs are tapes. No song is a disc. |
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Answer: Option A Explanation: Since each combination of premises shall contain two particular premises, no definite conclusion can be drawn. However, I and IV involve the extreme terms of the second and third premises and form a complementary pair. Thus, either I or IV follows. |
| 4. | Statements: Some papers are cats. All cats are bats. No bat is horse. Conclusions: Some papers are horses. No horse is cat. Some bats are papers. All papers are bats. |
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Answer: Option B Explanation: Some papers are cats. All cats are bats. Since one premise is particular, the conclusion must be particular and should not contain the middle term. So, it follows that 'Some papers are bats'. III is the converse of this conclusion and so it holds. All cats are bats. No bat is horse. 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 cat is horse'. II is the converse of this conclusion and so it holds. Some papers are bats. No bat is horse. 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 papers are not horses'. |
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Answer: Option A Explanation: No toy is building. All buildings are windows. Since the middle term 'buildings' is distributed twice and one premise is negative, the conclusion must be particular negative and should not contain the middle term. So, it follows that 'Some windows are not toys'. Some tigers are toys. No toy is building. Since one premise is particular and the other premise is negative, the conclusion must be particular negative and should not contain the middle term. So, it follows that 'Some tigers are not buildings'. |
| 6. | Statements: No man is sky. No sky is road. Some men are roads. Conclusions: No road is man. No road is sky. Some skies are men All roads are men. |
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Answer: Option E Explanation: II is the converse of the second premise and so it holds. No man is sky. No sky is road. Since both the premises are negative, no definite conclusion follows. No man is sky. Some men are roads. 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 roads are not skies'. No sky is road. Some men are roads. As discussed above, it follows that 'Some men are not skies'. Hence, only II follows. |
| 7. | Statements: No paper is pen. No pen is pencil. All erasers are papers. Conclusions: Some papers are erasers. No pencil is eraser. No pen is eraser. All papers are erasers. |
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Answer: Option E Explanation: I is the converse of the third premise and so it holds. No paper is pen. No pen is pencil. Since both the premises are negative, no definite conclusion follows. All erasers are papers. No paper is pen. 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 eraser is pen'. III is the converse of this conclusion and so it holds. Hence, only I and III follow. |
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Answer: Option C Explanation: III is the converse of first premise and so it holds. All myths are fictions. No fiction is novel. 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 myth is novel'. Thus, I follows. No fiction is novel. All novels are stories. Since the middle term 'novels' is distributed twice in the premises, the conclusion must be particular. Since one premise is negative, the conclusion must be negative. So, it follows that 'Some stories are not fictions'. Hence, only I and III follow. |