# Discrete Mathematics Questions and Answers – Functions

This section focuses on "Functions" in Discrete Mathematics. These Multiple Choice Questions (mcq) should be practiced to improve the Discrete Mathematics skills required for various interviews (campus interviews, walk-in interviews, company interviews), placements, entrance exams and other competitive examinations.

1. A function or mapping (Defined as f:X->Y) is a relationship from elements of one set X to elements of another set Y, then X is called?

A. Codomain

B. pre-image

C. Domain

D. image of function

View Answer

Ans : C

Explanation: A function or mapping (Defined as f:X->Y) is a relationship from elements of one set X to elements of another set Y (X and Y are non-empty sets). X is called Domain

2. A function can not be?

A. one to one

B. many to one

C. one to many.

D. All of the above

View Answer

Ans : C

Explanation: A function can be one to one or many to one but not one to many.

3. f:N->N,f(x)=5x is?

A. injective

B. not injective

C. surjective

D. inverse

View Answer

Ans : A

Explanation: f:N->N,f(x)=5x is injective.

4. A function f:A→B is ___________ (onto) if the image of f equals its range.

A. injective

B. surjective

C. inverse

D. not surjective

View Answer

Ans : B

Explanation: A function f:A->B is surjective (onto) if the image of f equals its range.

5. If function is both surjective and injective then it is known as?

A. invertible

B. composition

C. bijective

D. associative

View Answer

Ans : C

Explanation: f is both surjective and injective, we can say f is bijective.

6. If f and g are onto then the function (gof) is?

A. one to one

B. onto

C. one to many.

D. into

View Answer

Ans : B

Explanation: If f and g are onto then the function (gof) is also onto.

7. Composition does not hold?

A. associative property

B. commutative property

C. one-to-one function

D. Both A and B

View Answer

Ans : B

Explanation: Composition always holds associative property but does not hold commutative property.

8. Let f and g be the function from the set of integers to itself, defined by f(x) = 2x + 1 and g(x) = 3x + 4. Then the composition of f and g is ____________

A. 6x+9

B. 6x+7

C. 6x+3

D. 6x+8

View Answer

Ans : A

Explanation: The composition of f and g is given by f(g(x)) which is equal to 2(3x + 4) + 1

9. __________ bytes are required to encode 2000 bits of data.

A. 4

B. 8

C. 1

D. 2

View Answer

Ans : D

Explanation: Two bytes are required to encode 2000 (actually with 2 bytes you can encode up to and including 65,535.

10. which of the following is true?

A. The function f(x) = x^3 is bijection from R to R.

B. The function f(x)=x+1 from the set of integers to itself is onto.

C. Both A and B

D. None of the above

View Answer

Ans : C

Explanation: Both A and B the following is true.

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