Question

If A X B = {(1, a), (1, b), (1, c), (2, a), (2, b), (2, c)} then find set A.

(a) {1}

(b) {1, 2}

(c) {1, a}

(d) {a, b, c}

The question was posed to me in semester exam.

This interesting question is from Cartesian Product of Sets topic in portion Relations and Functions of Mathematics – Class 11

Answer 1

The correct option is (b) {1, 2}

Easy explanation: In each ordered pair of A X B, first element belongs to set A and second element belongs to set B.

1,2 ∈ A so, A = {1, 2}.