JEE Main Mathematics - Unit 1: Sets, Relations and Functions - Practice Test (100 MCQs)

JEE Main Mathematics - Unit 1: Sets, Relations and Functions - Practice Test (100 MCQs)

JEE Main Mathematics - Unit 1: Sets, Relations and Functions - Practice Test (100 MCQs)

Targeted 100 MCQ Practice Module focusing on: Sets and their representation; Union, intersection and complement of sets and their algebraic properties; Power set; Relations, types of relations, equivalence relations, functions; one-one, into and onto functions; the composition of functions.

Select your answers and click Submit Assessment Answers at the bottom to calculate your total score and review explanations.

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SECTION I: Sets - Basic Concepts and Representation [Questions 1 to 10]
1. A well-defined collection of distinct objects is called a:
Explanation: A set is a well-defined collection of distinct objects, considered as an object in its own right.
2. Which symbol denotes 'is an element of' in set theory?
Explanation: The symbol ∈ is read as 'belongs to' or 'is an element of'.
3. The set {1, 2, 3, 4, 5} written in set-builder form is:
Explanation: Natural numbers from 1 to 5 satisfy x ∈ N and x ≤ 5.
4. A set containing no element at all is called a:
Explanation: A set with no elements is called the null set (or empty set), denoted by ∅ or { }.
5. If A = {x : x² = 9, x ∈ N}, then A is:
Explanation: x² = 9 gives x = 3 or x = -3, but since x ∈ N, only x = 3 qualifies, so A = {3}.
6. Which of the following is an example of an infinite set?
Explanation: The set of natural numbers N = {1, 2, 3, ...} continues indefinitely and hence is infinite.
7. Two sets A and B are said to be equal if:
Explanation: Sets A and B are equal only when they contain exactly the same elements, i.e., A ⊆ B and B ⊆ A.
8. A set having exactly one element is called a:
Explanation: A set with precisely one element, such as {5}, is called a singleton set.
9. Two finite sets are called equivalent if:
Explanation: Equivalent sets need not have identical elements; they simply must have equal cardinality, i.e., n(A) = n(B).
10. The set {x : x is a letter in the word 'SCHOOL'} in roster form is:
Explanation: Roster form lists distinct elements only, so repeated letters like 'O' are written once: {S, C, H, O, L}.
SECTION II: Union, Intersection, Difference and Complement [Questions 11 to 20]
11. If A = {1, 2, 3, 4} and B = {3, 4, 5, 6}, then A ∪ B is:
Explanation: A ∪ B contains all elements present in A or B or both, taken without repetition: {1,2,3,4,5,6}.
12. If A = {1, 2, 3, 4} and B = {3, 4, 5, 6}, then A ∩ B is:
Explanation: A ∩ B contains elements common to both sets, i.e., {3, 4}.
13. If A = {1, 2, 3, 4} and B = {3, 4, 5, 6}, then A − B is:
Explanation: A − B consists of elements of A that are not in B, i.e., {1, 2}.
14. If U = {1,2,3,...,10} is the universal set and A = {2,4,6,8,10}, then A′ (complement of A) is:
Explanation: The complement of A consists of elements of U not in A, i.e., the odd numbers {1,3,5,7,9}.
15. Two sets A and B are called disjoint if:
Explanation: Disjoint sets have no elements in common, so their intersection is the empty set.
16. For any set A, A ∪ A′ equals:
Explanation: A set together with its complement covers the entire universal set: A ∪ A′ = U.
17. For any set A, A ∩ A′ equals:
Explanation: A set and its complement share no common elements, so A ∩ A′ = ∅.
18. If A ⊂ B, then A ∪ B equals:
Explanation: When A is a subset of B, every element of A is already in B, so their union is simply B.
19. If A ⊂ B, then A ∩ B equals:
Explanation: When A ⊆ B, the elements common to both sets are exactly the elements of A.
20. If n(A) = 20, n(B) = 15 and n(A ∩ B) = 5, then n(A ∪ B) is:
Explanation: Using n(A ∪ B) = n(A) + n(B) − n(A ∩ B) = 20 + 15 − 5 = 30.
SECTION III: Algebraic Properties of Sets and De Morgan's Laws [Questions 21 to 30]
21. Which law states that A ∪ (B ∩ C) = (A ∪ B) ∩ (A ∪ C)?
Explanation: This is the distributive law of union over intersection.
22. Which law states that A ∩ (B ∪ C) = (A ∩ B) ∪ (A ∩ C)?
Explanation: This is the distributive law of intersection over union.
23. According to De Morgan's Law, (A ∪ B)′ equals:
Explanation: De Morgan's first law states that the complement of a union equals the intersection of the complements: (A ∪ B)′ = A′ ∩ B′.
24. According to De Morgan's Law, (A ∩ B)′ equals:
Explanation: De Morgan's second law states that the complement of an intersection equals the union of the complements: (A ∩ B)′ = A′ ∪ B′.
25. The property A ∪ B = B ∪ A illustrates which law of set operations?
Explanation: Since the order of the sets does not affect the union, this illustrates the Commutative Law.
26. The property (A ∪ B) ∪ C = A ∪ (B ∪ C) illustrates which law?
Explanation: Grouping of sets does not change the result of repeated unions, illustrating the Associative Law.
27. For any set A, A ∪ ∅ equals:
Explanation: The Identity Law states that the union of a set with the empty set leaves the set unchanged: A ∪ ∅ = A.
28. For any set A, A ∩ U equals (where U is the universal set):
Explanation: The Identity Law for intersection states A ∩ U = A.
29. The law A ∪ A = A and A ∩ A = A is called the:
Explanation: Combining a set with itself under union or intersection leaves it unchanged, which is the Idempotent Law.
30. The law A ∪ (A ∩ B) = A is known as the:
Explanation: This identity, where a set 'absorbs' the intersection term, is known as the Absorption Law.
SECTION IV: Power Set, Subsets and Cartesian Product [Questions 31 to 40]
31. The collection of all subsets of a set A is called the:
Explanation: The power set of A, denoted P(A), is the set of all possible subsets of A, including ∅ and A itself.
32. If a set A has n elements, the number of elements in its power set P(A) is:
Explanation: A set with n elements has 2^n subsets, so |P(A)| = 2^n.
33. If A = {1, 2}, then P(A) is:
Explanation: The power set of A = {1,2} includes the empty set, both singletons, and the set itself: {∅, {1}, {2}, {1,2}}.
34. The empty set ∅ is a subset of:
Explanation: By convention, the empty set is a subset of every set, including itself.
35. If A has 3 elements and B has 4 elements, the number of elements in A × B (Cartesian product) is:
Explanation: The number of elements in A × B equals n(A) × n(B) = 3 × 4 = 12.
36. If (x+1, y-2) = (3, 1) as an ordered pair, then the values of x and y are:
Explanation: Equating corresponding components: x+1=3 gives x=2, and y-2=1 gives y=3.
37. If n(A) = 5, the number of proper subsets of A is:
Explanation: Total subsets = 2^5 = 32; excluding the set A itself (proper subsets), we get 32 − 1 = 31.
38. A × (B ∪ C) is equal to:
Explanation: The Cartesian product distributes over union: A × (B ∪ C) = (A × B) ∪ (A × C).
39. If A = ∅, then the power set P(A) is:
Explanation: Even the empty set has one subset — itself — so P(∅) = {∅}, which has 2^0 = 1 element.
40. If A ⊆ B and B ⊆ A, then which of the following must be true?
Explanation: Mutual containment (A ⊆ B and B ⊆ A) is precisely the condition for two sets to be equal.
SECTION V: Relations - Definitions and Types [Questions 41 to 50]
41. A relation R from set A to set B is defined as:
Explanation: A relation R from A to B is any subset of the Cartesian product A × B.
42. If n(A) = 3 and n(B) = 4, the total number of relations that can be defined from A to B is:
Explanation: Since there are n(A)×n(B) = 12 ordered pairs in A × B, the total number of relations (subsets) is 2^12.
43. A relation R on set A is called reflexive if:
Explanation: Reflexivity requires every element to be related to itself: (a, a) ∈ R for all a ∈ A.
44. A relation R on set A is called symmetric if:
Explanation: Symmetry means whenever a is related to b, b must also be related to a.
45. A relation R on set A is called transitive if:
Explanation: Transitivity means if a is related to b and b is related to c, then a must be related to c.
46. Let R = {(1,1), (2,2), (3,3)} be a relation on A = {1,2,3}. R is:
Explanation: R contains (a,a) for every element (reflexive), trivially satisfies symmetry, and trivially satisfies transitivity.
47. The relation R = {(1,2), (2,1)} on A = {1,2,3} is:
Explanation: R is symmetric since (1,2) and (2,1) both appear, but it is not reflexive as (3,3) ∉ R (and (1,1), (2,2) are also missing).
48. A relation which is reflexive, symmetric, but not necessarily transitive is called:
Explanation: A relation satisfying only reflexivity and symmetry (without requiring transitivity) is termed a tolerance relation.
49. The relation 'is less than' (<) defined on the set of real numbers is:
Explanation: '<' is transitive (a<b, b<c ⟹ a<c) but not reflexive (a < a is false) and not symmetric (a<b does not imply b<a).
50. A relation R on a set A is called an antisymmetric relation if:
Explanation: Antisymmetry requires that if both (a,b) and (b,a) belong to R, then a must equal b.
SECTION VI: Equivalence Relations [Questions 51 to 60]
51. A relation that is reflexive, symmetric, and transitive is called:
Explanation: By definition, a relation satisfying all three properties—reflexivity, symmetry, and transitivity—is an equivalence relation.
52. The relation 'is congruent to' defined on the set of all triangles in a plane is:
Explanation: Congruence of triangles is reflexive (a triangle is congruent to itself), symmetric, and transitive, so it is an equivalence relation.
53. The relation 'is parallel to' defined on the set of all lines in a plane (assuming every line is parallel to itself) is:
Explanation: Parallelism is reflexive (each line parallel to itself), symmetric, and transitive, making it an equivalence relation.
54. For an equivalence relation R on set A, the equivalence class of element a is defined as:
Explanation: The equivalence class of a, denoted [a], consists of all elements related to a under R.
55. The equivalence classes formed by an equivalence relation on a set A always:
Explanation: A fundamental property of equivalence relations is that their equivalence classes partition the set into mutually disjoint, exhaustive subsets.
56. Let R be a relation on the set of integers Z defined by aRb if a − b is divisible by 5. R is:
Explanation: This 'congruence modulo 5' relation is reflexive, symmetric, and transitive, hence an equivalence relation.
57. For the equivalence relation 'congruence modulo n' on Z, the number of distinct equivalence classes is:
Explanation: Congruence modulo n partitions Z into exactly n equivalence classes: [0], [1], ..., [n-1].
58. The relation R = {(a,b) : a, b ∈ Z, a = b} on the set of integers is called the:
Explanation: The relation where each element is related only to itself (a = b) is the identity relation.
59. The relation R = A × A on a set A is called the:
Explanation: When every element of A is related to every element of A, R equals A × A, called the universal relation.
60. If R and S are two equivalence relations on a set A, then R ∩ S is:
Explanation: The intersection of two equivalence relations retains reflexivity, symmetry, and transitivity, and is therefore also an equivalence relation.
SECTION VII: Functions - Basic Concepts, Domain and Range [Questions 61 to 70]
61. A function f from set A to set B is a relation in which:
Explanation: By definition, a function assigns exactly one (unique) image in B to every element of A.
62. For a function f : A → B, the set A is called the:
Explanation: The set A, from which inputs of the function are taken, is called the domain.
63. For a function f : A → B, the set B is called the:
Explanation: The set B, which contains all possible outputs, is called the codomain of the function.
64. The range of a function f : A → B is:
Explanation: The range is the actual set of output values obtained, which is a subset of (or equal to) the codomain B.
65. The domain of the real function f(x) = 1/(x-3) is:
Explanation: The function is undefined when x − 3 = 0, i.e., x = 3, so the domain excludes 3: R − {3}.
66. The domain of the real function f(x) = √(x − 5) is:
Explanation: For the square root to be defined (real-valued), we need x − 5 ≥ 0, i.e., x ≥ 5, giving domain [5, ∞).
67. If f(x) = x², the range of f when the domain is R (the set of all real numbers) is:
Explanation: Since x² is always non-negative for real x, the range consists of all non-negative real numbers, [0, ∞).
68. Which of the following is NOT a function from A = {1,2,3} to B = {4,5,6}?
Explanation: In option C, the element 1 has two images (4 and 5), which violates the uniqueness requirement of a function.
69. A function in which the domain and codomain are both subsets of real numbers is called a:
Explanation: A function whose domain and codomain are subsets of R is called a real-valued function of a real variable, or simply a real function.
70. If f(x) = 3x + 2, then f(2) is:
Explanation: Substituting x = 2: f(2) = 3(2) + 2 = 6 + 2 = 8.
SECTION VIII: One-One (Injective) Functions [Questions 71 to 80]
71. A function f : A → B is called one-one (injective) if:
Explanation: Injectivity means no two distinct inputs map to the same output: f(a1) = f(a2) implies a1 = a2.
72. The function f : R → R defined by f(x) = 2x + 1 is:
Explanation: If f(x1) = f(x2), then 2x1+1 = 2x2+1, which gives x1 = x2, so f is one-one.
73. The function f : R → R defined by f(x) = x² is:
Explanation: f(2) = 4 and f(-2) = 4 shows that two distinct inputs give the same output, so f is not one-one.
74. If f : A → B is one-one, then which of the following must be true?
Explanation: For a one-one function between finite sets, the domain cannot have more elements than the codomain: n(A) ≤ n(B).
75. The function f : N → N defined by f(x) = x + 5 is:
Explanation: If x1 + 5 = x2 + 5, then x1 = x2, so distinct inputs always give distinct outputs, meaning f is one-one.
76. A one-one function is also known as a/an:
Explanation: The term 'injective' is synonymous with 'one-one'.
77. Graphically, a function f(x) is one-one if:
Explanation: The Horizontal Line Test states that a function is one-one if no horizontal line intersects its graph more than once.
78. If A = {1, 2} and B = {a, b, c}, the number of one-one functions from A to B is:
Explanation: The number of one-one functions from a set of 2 elements to a set of 3 elements is P(3,2) = 3 × 2 = 6.
79. The function f : R → R defined by f(x) = |x| is:
Explanation: Since f(1) = 1 and f(-1) = 1, two distinct values produce the same output, so f is not one-one.
80. A strictly increasing (or strictly decreasing) function on its domain is always:
Explanation: A strictly monotonic function never repeats a value, so distinct inputs always yield distinct outputs, making it one-one.
SECTION IX: Onto and Into Functions, Bijections [Questions 81 to 90]
81. A function f : A → B is called onto (surjective) if:
Explanation: Surjectivity means the range of f equals the entire codomain B, i.e., every element of B is 'hit' by some element of A.
82. A function f : A → B is called an into function if:
Explanation: An into function does not cover the entire codomain; its range is a proper subset of B.
83. The function f : R → R defined by f(x) = x³ is:
Explanation: f(x) = x³ is strictly increasing (hence one-one) and covers all real numbers as x ranges over R (hence onto), so it is bijective.
84. Consider f : R → R+ ∪ {0} defined by f(x) = x² (with restricted codomain). This function is:
Explanation: Restricting the codomain to non-negative reals, every value y ≥ 0 has a pre-image (x = √y), so f becomes onto (though still not one-one).
85. A function which is both one-one and onto is called a:
Explanation: A function satisfying both injectivity and surjectivity is called a bijective function or bijection.
86. If f : A → B is onto and A, B are finite sets, then:
Explanation: For an onto function between finite sets, the codomain cannot have more elements than the domain: n(B) ≤ n(A).
87. The function f : R → R defined by f(x) = 5 (a constant function) is:
Explanation: A constant function maps every input to the single value 5, so it is neither one-one nor onto—it is an into function.
88. If A = {1,2,3} and B = {1,2}, the number of onto functions from A to B is:
Explanation: Total functions from A to B = 2³ = 8. Subtracting the 2 constant (non-onto) functions gives 8 − 2 = 6 onto functions.
89. The function f : Z → Z defined by f(x) = 2x is:
Explanation: f is one-one (2x1=2x2 ⟹ x1=x2), but odd integers in the codomain Z are never obtained as 2x for integer x, so f is not onto.
90. If f : A → B is a bijection, then which of the following is true?
Explanation: Only a bijective function has a well-defined inverse function, and that inverse is itself a bijection.
SECTION X: Composition of Functions and Inverse Functions [Questions 91 to 100]
91. If f : A → B and g : B → C are two functions, their composition gof : A → C is defined by:
Explanation: The composite function gof is defined as gof(x) = g(f(x)), applying f first and then g.
92. If f(x) = x + 2 and g(x) = 3x, then (gof)(x) is:
Explanation: (gof)(x) = g(f(x)) = g(x+2) = 3(x+2) = 3x + 6.
93. If f(x) = x + 2 and g(x) = 3x, then (fog)(x) is:
Explanation: (fog)(x) = f(g(x)) = f(3x) = 3x + 2.
94. In general, for two functions f and g, gof and fog are:
Explanation: Function composition is generally not commutative: gof ≠ fog in most cases.
95. The composition of two one-one functions is always:
Explanation: If f and g are both one-one, then gof is also one-one, since distinct inputs remain distinct through both mappings.
96. The composition of two onto functions is always:
Explanation: If f and g are both onto, their composition gof is also onto, since every element of the final codomain has a pre-image.
97. A function f : A → A defined by f(x) = x for every x ∈ A is called the:
Explanation: The function that maps every element to itself is called the identity function, usually denoted I(x) = x.
98. If f : A → B is a bijection with inverse f⁻¹ : B → A, then f⁻¹of equals:
Explanation: By definition of inverse functions, f⁻¹of(x) = x for all x ∈ A, i.e., f⁻¹of = I_A, the identity function on A.
99. If f(x) = 2x + 3, then f⁻¹(x) is:
Explanation: Setting y = 2x+3 and solving for x gives x = (y−3)/2, so f⁻¹(x) = (x−3)/2.
100. For composition of functions to be defined for gof, it is necessary that:
Explanation: gof is defined only when the outputs (range) of f can be validly taken as inputs of g, i.e., range of f ⊆ domain of g.

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