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Quiz: Logical Deduction - Section 2

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Number of Questions: 11

Question: 1 -

Statements: Some books are pens. No pen is pencil.

Conclusions:

  1. Some pens are books.
  2. Some pencils are books.
  3. Some books are not pencils.
  4. All pencils are books.

Options:

  1. Only I follows

  2. Only I and II follow

  3. Only I and III follow

  4. Only II and III follow

    5. Answer:

    Only I and III follow
    Solution:

    Since one premise is particular and the other negative, the conclusion must be particular negative and should not contain the middle term. Thus, III follows. I is the converse of the first premise and so it also holds.

Question: 2 -

Statements: Some bottles are drinks. All drinks are cups.

Conclusions:

  1. Some bottles are cups.
  2. Some cups are drinks.
  3. All drinks are bottles.
  4. All cups are drinks.

Options:

  1. Only II and IV follow

  2. Only II and III follow

  3. Only I and IV follow

  4. Only I and II follow

    5. Answer:

    Only I and II follow
    Solution:

    Since one premise is particular, the conclusion must be particular and should not contain the middle term. So, it follows that 'Some bottles are cups'. Thus, I follows. II is the converse of the second premise and so it also holds. 

Question: 3 -

Statements: Some tables are TVs. Some TVs are radios.

Conclusions:

  1. Some tables are radios.
  2. Some radios are tables.
  3. All radios are TVs.
  4. All TVs are tables.

Options:

  1. Only II and IV follow

  2. Only I and III follow

  3. None follows

  4. All follow

    5. Answer:

    None follows
    Solution:

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

Question: 4 -

Statements: Some taxis have horns. Some taxis have lights.

Conclusions:

  1. Every taxi has either horn or light.
  2. Some taxis have neither light nor horn.
  3. Some taxis have horns as well as lights.
  4. No taxi has horn as well as light.

Options:

  1. Only II and III follow

  2. Only I and II follow

  3. Only II and IV follow

  4. Either III or IV follows

    5. Answer:

    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.

Question: 5 -

Statements: All terrorists are guilty. All terrorists are criminals.

Conclusions:

  1. Either all criminals are guilty or all guilty are criminals.
  2. Some guilty persons are criminals.
  3. Generally criminals are guilty.
  4. Crime and guilt go together.

Options:

  1. Only I follows

  2. Only I and III follow

  3. Only II follows

  4. Only II and IV follow

    5. Answer:

    Only II follows
    Solution:

    Since the middle term 'terrorists' is distributed twice in the premises, the conclusion cannot be universal. So, it follows that 'Some guilty persons are criminals'. Thus, II holds.