Question

Let A be the set of all 25 students of Class X in a school. Let : A → N be
function defined by () = roll number of the student . Then is:

• A. one-one but not onto
• B. one-one
• C. onto but not one-one
• D. many one

Answer 1

The correct option is A

one-one but not onto

No two different students of the class can have same roll number. Therefore,

must be one-one.

Also, there are 25 students and 25 roll numbers , so that 26 can not be the image of any element of X under . Hence, is not onto.