Discrete Mathematics Multiple Choice Questions 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
Answer: d
Clarification: 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
Answer: a
Clarification: 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}
Answer: c
Clarification: Set should include 1 or an odd multiple of 5.
4. Express {x: x= n/ (n+1), n is a natural number less than 7} in roster form.
a) {1⁄2, 2⁄3, 4⁄5, 6⁄7}
b) {1⁄2, 2⁄3, 3⁄4, 4⁄5, 5⁄6, 6⁄7, 7⁄8}
c) {1⁄2, 2⁄3, 3⁄4, 4⁄5, 5⁄6, 6⁄7}
d) Infinite set
Answer: c
Clarification: n/(n+1) = 1/(1+1) = 1⁄2 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
Answer: b
Clarification: 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
Answer: d
Clarification: 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
Answer: c
Clarification: Empty set is a subset of every set.
8. Subset of the set A= { } is?
a) A
b) {}
c) ∅
d) All of the mentioned
Answer: d
Clarification: 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
Answer: a
Clarification: 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) {∅}
Answer: c
Clarification: 2 and 3 are the divisors of 72 which are prime.