This set of Discrete Mathematics Interview Questions and Answers focuses on “Set Operations – 2”.

1. Let the set A is {1, 2, 3} and B is {2, 3, 4}. Then number of elements in A U B is

a) 4

b) 5

c) 6

d) 7

View Answer

Explanation: AUB is {1, 2, 3, 4}.

2. Let the set A is {1, 2, 3} and B is { 2, 3, 4}. Then number of elements in A ∩ B is

a) 1

b) 2

c) 3

d) 4

View Answer

Explanation: A ∩ B is {2, 3}.

3. Let the set A is {1, 2, 3} and B is {2, 3, 4}. Then the set A – B is

a) {1, -4}

b) {1, 2, 3}

c) {1}

d) {2, 3}

View Answer

Explanation: In A – B the common elements get cancelled.

4. In which of the following sets A- B is equal to B – A

a) A= {1, 2, 3}, B ={2, 3, 4}

b) A= {1, 2, 3}, B ={1, 2, 3, 4}

c) A={1, 2, 3}, B ={2, 3, 1}

d) A={1, 2, 3, 4, 5, 6}, B ={2, 3, 4, 5, 1}

View Answer

Explanation: A- B= B-A = Empty set.

5. Let A be set of all prime numbers, B be the set of all even prime numbers, C be the set of all odd prime numbers, then which of the following is true?

a) A ≡ B U C

b) B is a singleton set.

c) A ≡ C U {2}

d) All of the mentioned

View Answer

Explanation: 2 is the only even prime number.

6. If A has 4 elements B has 8 elements then the minimum and maximum number of elements in A U B are respectively

a) 4, 8

b) 8, 12

c) 4, 12

d) None of the mentioned

View Answer

Explanation: Minimum would be when 4 elements are same as in 8, maximum would be when all are distinct.

7. If A is {{Φ}, {Φ, {Φ}}, then the power set of A has how many element?

a) 2

b) 4

c) 6

d) 8

View Answer

Explanation: The set A has got 2 elements so n(P(A))=4.

8. Two sets A and B contains a and b elements respectively .If power set of A contains 16 more elements than that of B, value of ‘b’ and ‘a’ are respectively

a) 4, 5

b) 6, 7

c) 2, 3

d) None of the mentioned

View Answer

Explanation: 32-16=16, hence a=5, b=4.

9. Let A be {1, 2, 3, 4}, U be set of all natural numbers, then U-A’(complement of A) is given by set.

a) {1, 2, 3, 4, 5, 6, ….}

b) {5, 6, 7, 8, 9, ……}

c) {1, 2, 3, 4}

d) All of the mentioned

View Answer

Explanation: U – A’ ≡ A.

10. Which sets are not empty?

a) {x: x is a even prime greater than 3}

b) {x : x is a multiple of 2 and is odd}

c) {x: x is an even number and x+3 is even}

d) { x: x is a prime number less than 5 and is odd}

View Answer

Explanation: Because the set is {3}.

**Sanfoundry Global Education & Learning Series – Discrete Mathematics.**

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