Question

Which of the following statements is the negation of the statements “4 is odd or -9 is positive”?

(a) 4 is even or -9 is not negative

(b) 4 is odd or -9 is not negative

(c) 4 is even and -9 is negative

(d) 4 is odd and -9 is not negative

I have been asked this question during an interview for a job.

My question comes from Logics and Proofs topic in chapter The Foundation: Logics and Proofs of Discrete Mathematics

Answer 1

Right option is (c) 4 is even and -9 is negative

The explanation: Using  De Morgan’s Law  ~(A V B) ↔ ~A ∧ ~B.