Discrete Mathematics Questions and Answers for Aptitude test on “Cardinality of Sets”.
1. The cardinality of the set A = {1, 2, 3, 4, 6} is?
a) 5
b) 6
c) Integer
d) None of the mentioned
Answer: a
Clarification: 5, it is a number of elements in the sets.
2. For two equal sets there ___________
a) Cardinality is same
b) Cardinality is different
c) May be same or different
d) None of the mentioned
Answer: a
Clarification: Two equal sets should have the same number of elements.
3. If A is a subset of B then _______
a) The cardinality of A is greater than B
b) The cardinality of B is greater than A
c) Can’t say
d) None of the mentioned
Answer: b
Clarification: B contains all the elements of A, as well as other elements.
4. If there is a bijection between two sets A and B then _______
a) Cardinality of A is greater than B
b) Cardinality of B is greater than A
c) Cardinality of B is equal to A
d) None of the mentioned
Answer: c
Clarification: If there is bijection then two sets A and B will be equinumerous and thus will have same cardinality.
5. Let a set E ={0,2,4,6,8….} of non-negative even numbers and O = {1, 3, 5, 7, 9,…..} of non-negative odd numbers then?
a) Cardinality of set E is greater than that of O
b) Cardinality of set O is greater than that of E
c) Cardinality of set E is equal to that of O
d) None of the mentioned
Answer: c
Clarification: There is bijection then two sets E and O and they will be equinumerous and thus will have same cardinality.
6. Cardinality of the set of lower letter english alphabets is 26.
a) True
b) False
Answer: a
Clarification: From a, b, c…z there will be 26 elements.
7. Cardinality of the set of even prime number under 10 is 4.
a) True
b) False
Answer: b
Clarification: Since 2 is only even prime thus cardinality should be 1.
8. If for sets A and B there exists an injective function but not bijective function from A to B then?
a) Cardinality of A is strictly greater than B
b) Cardinality of B is strictly greater than A
c) Cardinality of B is equal to A
d) None of the mentioned
Answer: b
Clarification: If there doesnot exist a bijective function from A to B that means there are some elements in B whose preimage is not in A, thus cardinality of B is strictly greater than A.
9. If cardinality of (A U B) = cardinality of A+ cardinality of B. This means ____________
a) A is a subset of B
b) B is a subset of A
c) A and B are disjoint
d) None of the mentioned
Answer: c
Clarification: Thus if the cardinality of (A U B) = cardinality of A+ cardinality of B, it means they don’t have any element in common, n(A∩B) = 0.
10. If A is a subset of B and B is a subset of C, then cardinality of A U B U C is equal to ____________
a) Cardinality of C
b) Cardinality of B
c) Cardinality of A
d) None of the mentioned
Answer: a
Clarification: A U B U C = C, since a, b are subsets to C.