Question

If P X Q is an empty set then which of the following is a null set?

(a) only P

(b) only Q

(c) either P or Q

(d) both P and Q

This question was posed to me during an interview.

I'd like to ask this question from Cartesian Product of Sets topic in chapter Relations and Functions of Mathematics – Class 11

Answer 1

Right option is (c) either P or Q

To explain: If either set P or set Q is a null set then P X Q is an empty set.

i.e. if P is Φ or Q is Φ then P X Q = Φ.