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Consider the following statements. If D is dog, then D is very good. If D is very good, then D is dog. If D is not very good, then D is not a dog.

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Question

Consider the following statements.

  1. If D is dog, then D is very good.
  2. If D is very good, then D is dog.
  3. If D is not very good, then D is not a dog.
  4. If D is not a dog, then D is not very good. 

Identify the pairs of statements having the same meaning. Justify.

Sum
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Solution

Let p : D is dog.
q : D is very good.
Then the given statement in the symbolic form is

  1. p → q
  2. q → p
  3. ~q → ~p
  4. ~p → ~q
p q ~p ~q p → q q → p ~q → ~p ~p → ~q
T T F F T T T T
T F F T F T F T
F T T F T F T F
F F T T T T T T

Since the entries in (i) and (iii) columns are the same, they have the same meaning.

Also, the entries in (ii) and (iv) columns are the same. they have the same meaning.

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Chapter 1: Mathematical Logic - Miscellaneous Exercise 1 [Page 33]

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Balbharati Mathematics and Statistics 1 (Commerce) [English] Standard 12 Maharashtra State Board
Chapter 1 Mathematical Logic
Miscellaneous Exercise 1 | Q 4.19 | Page 33

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