NIELIT 2017 OCT Scientific Assistant A - Section A: 39

Question

Fact $1:$ All chickens are birds.

Fact $2:$ Some chickens are hens.

Fact $3:$ Female birds lay eggs.

If the first three statements are facts, which of the following statements must also be a fact?

1. All birds lay eggs.
2. Hens are birds.
3. Some chickens are not hens.

 

• A. II only
• B. II and III only
• C. I,II and III
• D. None of the statements is a known fact

Answer 1

Fact 1: All chickens are birds.

Fact 2: Some chickens are hens.

Fact 3: Female birds lay eggs.

1. All birds lay eggs: Fact 3 says that female birds lay eggs. But we have no idea about male birds. So, this statement is not a fact,
2. Hens are birds. Fact 1 and 2 says that some birds (which are chicken) are hens. But it does not say that hens (by default “all” applies here) are birds. 
3. Some chickens are not hens. Fact 2 says that some chickens are hens. But this does not prove “some chickens are not hens” – that may or may not be true. If Fact 2 is written as “Not all chickens are hens” then this statement will be a fact.

A fact must be PROVABLE – no guess work.

None of the statements here is a fact.

Correct option: D

Answer 2

Only statement III. Some chickens are not hens must also be a fact.

which is not in the options.

I think in statement II they have missed the “Some” i.e. II. Some Hens are birds.

Comments

How did you conclude 3?

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In normal case there will be some(at least one) chicken that are not hens.

But in extreme case “Fact 2: Some chickens are hens” will be all chickens are hens.

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A “fact” is always an extreme case – nothing should make it false.

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If we do not get any clear outcome then only we go for extreme case.

In SYLLOGISM, we are looking for LN’s(Logical ‘necessity’), not LP’s(Logical ‘possibility’). We shall mark LP as an answer choice only in the absence of an LN.

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No. If you cant prove a statement it is NOT a fact.