NIMCET 2010 — Reasoning PYQ

Analysis of Options:

• (a) All dogs are mad. All sick persons are mad. So all sick persons are dogs.

  • Let $M$ be the set of mad things.

  • $\text{Dogs}\subset M$ and $\text{Sick persons}\subset M$.

  • Being in the same larger set ($M$) does not mean one subset belongs to the other. The conclusion is Invalid.

• (b) All oranges are black. All figs are oranges. So all figs are black.

  • Let $B$ be the set of black things, $O$ be oranges, and $F$ be figs.

  • Premise 1: $O\subset B$

  • Premise 2: $F\subset O$

  • Using the transitive property:

    $$F\subset O\text{ and }O\subset B⟹F\subset B$$

  • This means "All figs are black" is a Logically Valid conclusion.

• (c) All windows are dogs. Some doors are dogs. So all windows are doors.

  • $\text{Windows}\subset \text{Dogs}$. There is an intersection between $\text{Doors}$ and $\text{Dogs}$.

  • This does not prove that all windows are doors. The conclusion is Invalid.

• (d) No man can fly. No kite can fly. So all men are kites.

  • Let $F$ be the set of things that can fly.

  • $\text{Men}\cap F=\varnothing$ and $\text{Kites}\cap F=\varnothing$.

  • Having a common exclusion does not create an inclusion between Men and Kites. The conclusion is Invalid.

Conclusion:

In option (b), the conclusion is a direct logical result of the premises.

Correct Option: (b)