1Which formula correctly represents the Principle of Inclusion-Exclusion for two finite sets and ?
A.
B.
C.
D.
Correct Answer:
Explanation:According to the Principle of Inclusion-Exclusion, to find the size of the union of two sets, we add the sizes of the individual sets and subtract the size of their intersection to avoid double counting.
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2In a class of 50 students, 30 study Mathematics, 25 study Physics, and 15 study both. How many students study at least one of the subjects?
A.35
B.40
C.55
D.45
Correct Answer: 40
Explanation:Using , we get .
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3The Pigeonhole Principle states that if items are put into containers, with , then at least one container must contain:
A.Exactly 1 item
B.More than 1 item
C.No items
D.Exactly 2 items
Correct Answer: More than 1 item
Explanation:If the number of items () exceeds the number of containers (), at least one container must hold at least 2 items (i.e., more than 1).
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4According to the Generalized Pigeonhole Principle, if objects are placed into boxes, then there is at least one box containing at least how many objects?
A.
B.
C.
D.
Correct Answer:
Explanation:The Generalized Pigeonhole Principle states that at least one box contains at least objects, where is the ceiling function.
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5How many people must be in a room to guarantee that at least two of them were born in the same month?
A.12
B.13
C.24
D.365
Correct Answer: 13
Explanation:Here, the 'pigeons' are people and the 'holes' are months (12). Since , we need to guarantee a collision.
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6What is the minimum number of students required in a class to guarantee that at least 5 students have the same grade, assuming there are 4 possible grades (A, B, C, D)?
A.16
B.17
C.20
D.21
Correct Answer: 17
Explanation:Using the generalized pigeonhole principle: We need . The smallest integer satisfying this is derived from . Here .
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7Let . Which of the following is a relation on ?
A.
B.
C.
D.
Correct Answer:
Explanation:A relation on set must be a subset of the Cartesian product . All elements in the ordered pairs must belong to . The other options contain elements (like 4) not in , or are not sets of ordered pairs.
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8The Cartesian product of sets and , denoted , is defined as:
A.
B.
C.
D.
Correct Answer:
Explanation: is the set of all ordered pairs where the first element is from and the second is from .
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9A relation on set is reflexive if:
A.
B.
C.
D.
Correct Answer:
Explanation:Reflexivity requires that every element in the set is related to itself.
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10A relation is symmetric if:
A.
B.
C.
D. for all
Correct Answer:
Explanation:Symmetry means if is related to , then must be related to .
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11A relation is antisymmetric if:
A.
B.
C.
D.It is not symmetric
Correct Answer:
Explanation:Antisymmetry means that no two distinct elements are related to each other in both directions. If they are, the elements must be identical.
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12A relation is transitive if:
A.
B.
C.
D.
Correct Answer:
Explanation:Transitivity implies that if relates to and relates to , then relates to .
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13If set has elements, how many possible relations are there on ?
A.
B.
C.
D.
Correct Answer:
Explanation:The size of the Cartesian product is . A relation is a subset of . The number of subsets is .
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14Let be a relation represented by the matrix . If is reflexive, what must be true about ?
A.All entries are 1
B.All diagonal entries are 1
C.The matrix is symmetric
D.All off-diagonal entries are 0
Correct Answer: All diagonal entries are 1
Explanation:For a reflexive relation, for all , meaning the main diagonal of the adjacency matrix must consist entirely of 1s.
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15If the matrix represents a relation , then is symmetric if and only if:
A. is an identity matrix
B. (Transpose)
C. has all 1s on the diagonal
D. is a triangular matrix
Correct Answer: (Transpose)
Explanation:Symmetry implies , which corresponds to in the matrix. Thus, the matrix equals its transpose.
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16Given relations and on a set , the composition is defined as:
A.
B.
C.
D.
Correct Answer:
Explanation:The composition (read 'S after R') involves going from to via , and then from to via .
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17If and are the boolean matrices representing relations and , what matrix represents the composition ?
A. (Boolean OR)
B. (Boolean AND)
C. (Boolean Product)
D. (Boolean Product)
Correct Answer: (Boolean Product)
Explanation:The matrix for is the Boolean product of and (in that order, assuming row-column multiplication convention for composition from left to right relations).
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18The inverse of a relation , denoted , is defined as:
A.
B.
C.
D.The empty set
Correct Answer:
Explanation:The inverse relation simply reverses the ordered pairs of the original relation.
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19A relation on a set is an Equivalence Relation if it is:
A.Reflexive, Symmetric, and Transitive
B.Reflexive, Antisymmetric, and Transitive
C.Irreflexive, Symmetric, and Transitive
D.Symmetric and Transitive only
Correct Answer: Reflexive, Symmetric, and Transitive
Explanation:These are the three defining properties of an equivalence relation.
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20Which of the following is an equivalence relation on the set of integers ?
A.
B. is odd
C.
D. divides
Correct Answer:
Explanation:Congruence modulo is Reflexive (), Symmetric (), and Transitive. The others fail one or more properties.
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21The set of all elements related to an element in an equivalence relation is called:
A.The partition of
B.The equivalence class of , denoted
C.The power set of
D.The range of
Correct Answer: The equivalence class of , denoted
Explanation:The equivalence class contains all such that .
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22Equivalence classes of a relation on set form a:
A.Partition of
B.Subset of
C.Product of
D.Lattice
Correct Answer: Partition of
Explanation:Equivalence classes are disjoint and their union is the entire set , thus forming a partition.
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23A relation on a set is a Partial Ordering Relation (POSET) if it is:
Explanation:These are the three defining properties of a partial order.
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24Which of the following is a classic example of a Partial Ordering Relation?
A."is the father of" on a set of people
B."is a subset of" () on a power set
C."is friend of" on a set of people
D."rock, paper, scissors" dominance
Correct Answer: "is a subset of" () on a power set
Explanation:Subset inclusion is reflexive (), antisymmetric (), and transitive.
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25In a POSET , two elements and are called comparable if:
A.
B. or
C. and
D.They share an upper bound
Correct Answer: or
Explanation:Elements are comparable if one precedes the other in the ordering.
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26A POSET in which every pair of elements is comparable is called a:
A.Lattice
B.Total Ordering (or Chain)
C.Equivalence Relation
D.Well-ordered set
Correct Answer: Total Ordering (or Chain)
Explanation:A total order imposes a specific order on all pairs, unlike a partial order where some pairs may be incomparable.
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27What kind of graph is used to visualize a Partial Ordering Relation?
A.Scatter plot
B.Hasse Diagram
C.Pie Chart
D.Venn Diagram
Correct Answer: Hasse Diagram
Explanation:A Hasse diagram is a simplified directed graph that removes loops and transitive edges to visualize a partial order.
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28In a Hasse diagram, an edge is drawn from to (where is below ) if:
A. and there is no such that
B.
C.
D. and are incomparable
Correct Answer: and there is no such that
Explanation:This describes the 'covering' relation. Direct edges represent immediate precedence.
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29In a POSET, an element is maximal if:
A.For all ,
B.There is no element such that
C.It is the only element in the set
D.It is greater than all other elements
Correct Answer: There is no element such that
Explanation:A maximal element has nothing 'above' it. Note that there can be multiple maximal elements, whereas a 'maximum' element must be unique and comparable to all.
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30An element in a POSET is the Greatest Lower Bound (GLB) of a subset if:
A.It is an upper bound and smaller than any other upper bound
B.It is a lower bound and greater than any other lower bound
C.It is the smallest element in the subset
D.It is the largest element in the subset
Correct Answer: It is a lower bound and greater than any other lower bound
Explanation:GLB (infimum) is the unique element that is below the subset, but 'highest' among all such lower bounds.
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31A POSET is a Lattice if:
A.Every pair of elements has a Least Upper Bound and a Greatest Lower Bound
B.It is a total ordering
C.It has a unique maximum element
D.Every subset has a least element
Correct Answer: Every pair of elements has a Least Upper Bound and a Greatest Lower Bound
Explanation:This is the definition of a Lattice structure.
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32In the context of Lattices, the operation (Join) represents:
A.Greatest Lower Bound (GLB)
B.Least Upper Bound (LUB)
C.Set Intersection
D.Subtraction
Correct Answer: Least Upper Bound (LUB)
Explanation:The Join () corresponds to the Supremum or LUB of the two elements.
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33In the context of Lattices, the operation (Meet) represents:
A.Greatest Lower Bound (GLB)
B.Least Upper Bound (LUB)
C.Set Union
D.Addition
Correct Answer: Greatest Lower Bound (GLB)
Explanation:The Meet () corresponds to the Infimum or GLB of the two elements.
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34A Lattice is called Bounded if:
A.It has a finite number of elements
B.It has both a greatest element ($1$) and a least element ($0$)
C.It satisfies the distributive law
D.It is a subset of real numbers
Correct Answer: It has both a greatest element ($1$) and a least element ($0$)
Explanation:A bounded lattice must have a universal lower bound (0) and a universal upper bound (1).
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35A Sublattice is a subset of a lattice that:
A.Is a lattice itself under any operation
B.Is closed under the Join () and Meet () operations of the original lattice
C.Contains the top and bottom elements
D.Is a chain
Correct Answer: Is closed under the Join () and Meet () operations of the original lattice
Explanation:For a subset to be a sublattice, if are in the subset, then and (computed in the original lattice) must also be in the subset.
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36Which set with the relation 'divides' () forms a lattice?
A.
B. (Divisors of 6)
C.
D.
Correct Answer: (Divisors of 6)
Explanation:The divisors of an integer form a lattice under divisibility. For every pair (e.g., 2,3), there is a LCM (6) and GCD (1) within the set.
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37A relation is Irreflexive if:
A. for all
B. for some
C.
D.It is not reflexive
Correct Answer: for all
Explanation:Irreflexivity requires that NO element is related to itself (zero 1s on the diagonal of the matrix).
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38For the Principle of Inclusion-Exclusion with 3 sets, . What is ?
A.
B.
C.
D.
Correct Answer:
Explanation:The formula adds individual sizes (), subtracts pairwise intersections (), and adds the triple intersection ().
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39A Distributive Lattice is a lattice where:
A. holds
B.Every element has a complement
C.The order is total
D. implies
Correct Answer: holds
Explanation:This is the distributive law for lattices. The dual law (...) must also hold.
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40Which diagram represents the relation on the power set of ?
A.A triangle
B.A diamond (rhombus) shape
C.A straight line
D.A square with diagonals
Correct Answer: A diamond (rhombus) shape
Explanation:The power set is . is bottom, is top, and are in the middle, incomparable to each other.
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41The complement of a relation on set , denoted , is:
A.
B.
C.
D.The identity relation
Correct Answer:
Explanation:The complement relation contains all pairs in the Cartesian product that are NOT in .
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42Consider the relation on . Is it transitive?
A.Yes
B.No, because and are in , but is not
C.No, because it is symmetric
D.No, because is in
Correct Answer: No, because and are in , but is not
Explanation:For transitivity, if and , then must exist. Since , it is not transitive.
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43If is an equivalence relation on set , then the Quotient Set is:
A.The set of all equivalence classes
B.The set minus
C.The largest subset of
D.The intersection of all classes
Correct Answer: The set of all equivalence classes
Explanation:The quotient set is defined as the collection of all disjoint equivalence classes generated by .
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44In a Hasse diagram, if there is a path from to , then:
A. covers
B.
C.
D. and are equal
Correct Answer:
Explanation:Hasse diagrams are typically drawn with 'greater' elements higher up. A path upwards from to implies transitivity, so .
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45The relation 'less than' () on integers is:
A.Reflexive and Transitive
B.Irreflexive and Transitive
C.Symmetric and Transitive
D.Equivalence Relation
Correct Answer: Irreflexive and Transitive
Explanation: is false (Irreflexive). If and , then (Transitive).
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46Let be a lattice. For any , ?
A.$0$
B.$1$
C.
D.
Correct Answer:
Explanation:This is the Idempotent Law of lattices ( and ).
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47Consider a set . How many ordered pairs are in the Universal Relation on ?
A.3
B.6
C.9
D.
Correct Answer: 9
Explanation:The universal relation is , which has elements.
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48Which of the following properties does the Identity Relation satisfy?
A.Only Reflexive
B.Only Symmetric
C.Equivalence Relation and Partial Order
D.None of the above
Correct Answer: Equivalence Relation and Partial Order
Explanation:The identity relation () is Reflexive, Symmetric, Antisymmetric, and Transitive. It satisfies criteria for both equivalence and partial order.
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49If we represent a relation using a directed graph (digraph), a reflexive relation is characterized by:
A.No cycles
B.A self-loop on every vertex
C.Bidirectional edges
D.No edges
Correct Answer: A self-loop on every vertex
Explanation:Reflexivity means every element relates to itself, visualized as a loop from a vertex back to itself.
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50The Principle of Inclusion-Exclusion is used to calculate the cardinality of the:
A.Union of sets
B.Intersection of sets
C.Power set
D.Cartesian product
Correct Answer: Union of sets
Explanation:It is specifically designed to calculate by accounting for overlaps.
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