# Discrete Mathematics Questions and Answers – Types of Set

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This set of Discrete Mathematics Multiple Choice Questions & Answers (MCQs) focuses on “Types of Set”.

1. {x: x is an integer neither positive nor negative} is ________
a) Empty set
b) Non-empty set
c) Finite set
d) Non- empty and Finite set

Explanation: Set = {0} non-empty and finite set.

2. {x: x is a real number between 1 and 2} is an ________
a) Infinite set
b) Finite set
c) Empty set
d) None of the mentioned

Explanation: It is an infinite set as there are infinitely many real number between any two different real numbers.

3. Write set {1, 5, 15, 25,…} in set-builder form.
a) {x: either x=1 or x=5n, where n is a real number}
b) {x: either x=1 or x=5n, where n is a integer}
c) {x: either x=1 or x=5n, where n is an odd natural number}
d) {x: x=5n, where n is a natural number}

Explanation: Set should include 1 or an odd multiple of 5.
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4. Express {x: x= n/ (n+1), n is a natural number less than 7} in roster form.
a) {12, 23, 45, 67}
b) {12, 23, 34, 45, 56, 67, 78}
c) {12, 23, 34, 45, 56, 67}
d) Infinite set

Explanation: n/(n+1) = 1/(1+1) = 12 and n>7.

5. Number of power set of {a, b}, where a and b are distinct elements.
a) 3
b) 4
c) 2
d) 5

Explanation: Power set of {a, b} = {∅, {a, b}, {a}, {b}}.

6. Which of the following is subset of set {1, 2, 3, 4}?
a) {1, 2}
b) {1, 2, 3}
c) {1}
d) All of the mentioned

Explanation: There are total 16 subsets.

7. A = {∅,{∅},2,{2,∅},3}, which of the following is true?
a) {{∅,{∅}} ∈ A
b) {2} ∈ A
c) ∅ ⊂ A
d) 3 ⊂ A

Explanation: Empty set is a subset of every set.

8. Subset of the set A= { } is?
a) A
b) {}
c) ∅
d) All of the mentioned

Explanation: Every set is subset of itself and Empty set is subset of each set.

9. {x: x ∈ N and x is prime} then it is ________
a) Infinite set
b) Finite set
c) Empty set
d) Not a set

Explanation: There is no extreme prime, number of primes is infinite.

10. Convert set {x: x is a positive prime number which divides 72} in roster form.
a) {2, 3, 5}
b) {2, 3, 6}
c) {2, 3}
d) {∅}

Explanation: 2 and 3 are the divisors of 72 which are prime.

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