Question

Let A = {1, 2, 3} and B = {a, b} ,which of the following subsets of A $\times$ B is a mapping From A to B?

• A. {(1, a), (3, b), (2, a), (2, b)}
• B. {(1, b), (2, a), (3, a)}
• C. {(1, a), (2, b)}
• D. None of the above

Answer 1

The correct option is B {(1, b), (2, a), (3, a)}

(a) {(1, a), (3, b), (2, a), (2, b)} is not a mapping from A to B due to (2, a) and (2, b) as one element corresponding two images.
(a) {(1, b) (2, a) (3,a)} $\Rightarrow$ mapping as element in domain posses unique image in codomain.
(b) Is not a mapping as 3 does not corresponds any image.