NCERT Class 12-Mathematics: Chapter –1 Relations and Functions Part 4

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Objective Type Questions

Choose the Correct Answer from the Given Four Options in Each of the Examples 17 to 25

Question 17:

Let R be a relation on the set N of natural numbers defined by if divides . Then R is

(A) Reflexive and symmetric

(B) Transitive and symmetric

(C) Equivalence

(D) Reflexive, transitive but not symmetric

Answer:

The correct choice is (D).

Since n divides , R is reflexive. R is not symmetric since is transitive since for whenever and , i.e., divides and divides , then will divide .

Question 18:

Let L denote the set of all straight lines in a plane. Let a relation R be defined by if and only if is perpendicular to . Then R is

(A) Reflexive

(B) Symmetric

(C) Transitive

(D) None of these

Answer:

The correct choice is (B).

Question 19:

Let be the set of natural numbers and the function be defined by . Then is

(A) Surjective

(B) Injective

(C) Bijective

(D) None of these

Answer:

(B) Is the correct option.

Question 20:

Set A has elements and the set B has elements. Then the number of injective mappings that can be defined from A to B is

(A)

(B)

(C) 24

(D) 64

Answer:

The correct choice is (C).

The total number of injective mappings from the set containing elements into the set containing elements is .

Question 21:

Let be defined by and be defined by , then f is

(A)

(B)

(C)

(D)

Answer:

(C) is the correct choice.

Question 22:

Let be defined by . Then is given by

(A)

(B)

(C)

(D) None of these

Answer:

(A) Is the correct choice.

Question 23:

Let be defined by . Then, pre-images of and , respectively, are

(A)

(B)

(C)

(D)

Answer:

(C) Is the correct choice since for or and for and hence .

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