suppose we have a chair with n legs and it stands with all its legs touching d floor,regardless of floor quality,
i.e. smoothness,evenness etc.
then what is the value of n?
how should we go ahead in such questions?

my method is NOT advisable but this is how i thought if it - pyramids are known to be the most solid structure because of the triangular base i.e. 3 sides. hence, 3 legged chair.

These questions are mostly based on your presence of mind. Use elimination approach and be clear that the most obvious is also the least likely solution.

I think the 3 logic would work if the surface was a plane (as any three points can determine a plane). But the question states "regardless of floor quality", and that bit has thrown me off.