A proposition is a declarative statement that is either true or false. The statement is true.
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2What is the negation of the proposition "It is raining"?
propositional logic
Easy
A.It is cloudy.
B.It is sunny.
C.It may be raining.
D.It is not raining.
Correct Answer: It is not raining.
Explanation:
The negation of a proposition reverses its truth value. The negation of "It is raining" is "It is not raining."
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3The conjunction is true when:
propositional logic
Easy
A.Both and are true.
B.At least one of and is true.
C.Exactly one of and is true.
D.Both and are false.
Correct Answer: Both and are true.
Explanation:
The conjunction is true only when both component propositions are true.
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4Which symbol is commonly used for the universal quantifier?
first order logic
Easy
A.
B.
C.
D.
Correct Answer:
Explanation:
The symbol means "for all" and is called the universal quantifier.
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5Which symbol is commonly used for the existential quantifier?
first order logic
Easy
A.
B.
C.
D.
Correct Answer:
Explanation:
The symbol means "there exists" and is called the existential quantifier.
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6If , which statement is true?
sets
Easy
A.
B.
C.
D.
Correct Answer:
Explanation:
The element appears in the set , so .
Incorrect! Try again.
7What is the cardinality of the set ?
sets
Easy
A.
B.
C.
D.
Correct Answer:
Explanation:
The cardinality of a set is its number of distinct elements. Set has four elements.
Incorrect! Try again.
8What is the union of and ?
sets
Easy
A.
B.
C.
D.
Correct Answer:
Explanation:
The union contains every distinct element in either set. Therefore, .
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9A relation from a set to a set is a subset of:
relations
Easy
A.
B.
C.
D.
Correct Answer:
Explanation:
A relation from to is any subset of the Cartesian product .
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10A relation on a set is reflexive if:
relations
Easy
A.$ for every $a, b \in A$
B. implies
C. for every
D. and imply
Correct Answer: for every
Explanation:
A relation is reflexive when every element is related to itself, so for all .
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11A relation is symmetric if:
relations
Easy
A. implies
B. for every
C. implies
D. and imply
Correct Answer: implies
Explanation:
A relation is symmetric when reversing a related pair preserves the relation.
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12A function from to assigns each element of to:
functions
Easy
A.No elements of
B.Every element of
C.Exactly one element of
D.At least two elements of
Correct Answer: Exactly one element of
Explanation:
By definition, a function assigns every element of its domain exactly one value in its codomain.
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13The set of input values of a function is called its:
functions
Easy
A.Image
B.Range
C.Domain
D.Codomain
Correct Answer: Domain
Explanation:
The domain of a function is the set of all permitted input values.
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14A function is one-to-one if:
functions
Easy
A.All inputs have the same output.
B.The domain and codomain are equal.
C.Different inputs have different outputs.
D.Every output has several inputs.
Correct Answer: Different inputs have different outputs.
Explanation:
A one-to-one, or injective, function maps distinct domain elements to distinct codomain elements.
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15A partial order must be reflexive, antisymmetric, and:
partial orders
Easy
A.Transitive
B.Invertible
C.Symmetric
D.Periodic
Correct Answer: Transitive
Explanation:
A partial order is a relation that is reflexive, antisymmetric, and transitive.
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16Under the usual order on the integers, which pair is comparable?
partial orders
Easy
A. and
B. and
C. and
D. and
Correct Answer: and
Explanation:
Two elements are comparable if one is related to the other. Since , the integers and are comparable.
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17In a lattice, every pair of elements has a unique:
lattices
Easy
A.Maximum only
B.Inverse and identity
C.Least upper bound and greatest lower bound
D.Minimum only
Correct Answer: Least upper bound and greatest lower bound
Explanation:
A lattice is a partially ordered set in which every pair of elements has a least upper bound and a greatest lower bound.
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18The least upper bound of two elements is also called their:
lattices
Easy
A.Join
B.Complement
C.Inverse
D.Meet
Correct Answer: Join
Explanation:
The least upper bound is called the join, commonly written as .
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19Which property requires that a binary operation on a group be closed?
groups
Easy
A.Every group element has a different name.
B.The group must contain exactly two elements.
C.The operation must be commutative.
D.The result of two group elements is in the group.
Correct Answer: The result of two group elements is in the group.
Explanation:
Closure means that applying the operation to any two elements of the group produces another element of the same group.
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20Every group must contain an element called the:
groups
Easy
A.Largest element
B.Repeated element
C.Zero element
D.Identity element
Correct Answer: Identity element
Explanation:
The identity element leaves every group element unchanged under the group operation.
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21Which proposition is logically equivalent to ?
propositional logic
Medium
A.
B.
C.
D.
Correct Answer:
Explanation:
Since , its negation is .
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22The formula is false for which assignment?
propositional logic
Medium
A.
B.
C.
D.
Correct Answer:
Explanation:
For this assignment, is true, but is false, so their conjunction is false.
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23From the premises , , and , which conclusion follows?
propositional logic
Medium
A.
B.
C.
D.
Correct Answer:
Explanation:
From and , modus tollens gives . Then and give .
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24Let mean " is a student" and mean " passed." Which formula states that exactly one student passed?
first order logic
Medium
A.
B.
C.
D.
Correct Answer:
Explanation:
The formula asserts the existence of a student who passed and requires every student who passed to be that same individual.
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25What is the negation of ?
first order logic
Medium
A.
B.
C.
D.
Correct Answer:
Explanation:
Negating quantifiers changes to and to , while the predicate is also negated.
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26Given , , and , which statement must be true?
first order logic
Medium
A.
B.
C.
D.
Correct Answer:
Explanation:
An object satisfying must satisfy , and every object satisfying must satisfy . Thus at least one object satisfies .
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27In a class of 60 students, 35 study algebra, 28 study combinatorics, and 15 study both. How many study neither subject?
sets
Medium
A.
B.
C.
D.
Correct Answer:
Explanation:
By inclusion-exclusion, . Therefore, students study neither.
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28Let and . How many subsets of contain every element of ?
sets
Medium
A.
B.
C.
D.
Correct Answer:
Explanation:
The elements and must be included. Each of the remaining elements and may be included or excluded, giving subsets.
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29Define a relation on the integers by if and only if is divisible by . Which description of is correct?
relations
Medium
A.It is reflexive and transitive but not symmetric.
B.It is an equivalence relation with four classes.
C.It is reflexive and symmetric but not transitive.
D.It is symmetric and transitive but not reflexive.
Correct Answer: It is an equivalence relation with four classes.
Explanation:
Congruence modulo is reflexive, symmetric, and transitive. Its classes correspond to remainders .
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30Let and . Which pair belongs to , where when some satisfies and ?
relations
Medium
A.
B.
C.
D.
Correct Answer:
Explanation:
Since and , following two consecutive -steps gives .
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31A relation on is reflexive and contains and . If is also symmetric and transitive, which pair must it contain?
relations
Medium
A. only
B. only
C.
D. only
Correct Answer:
Explanation:
Transitivity applied to and requires . Symmetry also forces the reverse pairs, but the listed pair that must follow directly is .
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32For the function defined by , which property holds?
functions
Medium
A.It is surjective but not injective.
B.It is injective but not surjective.
C.It is both injective and surjective.
D.It is neither injective nor surjective.
Correct Answer: It is injective but not surjective.
Explanation:
Distinct integers give distinct outputs, so is injective. Its outputs are only odd integers, so it is not surjective onto .
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33Let be defined by and by . What is ?
functions
Medium
A.
B.
C.
D.
Correct Answer:
Explanation:
First apply : . Then apply : .
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34How many surjective functions are there from a three-element set to a two-element set?
functions
Medium
A.
B.
C.
D.
Correct Answer:
Explanation:
There are total functions. Excluding the two constant functions that miss one codomain element leaves surjections.
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35Consider the set ordered by divisibility. Which statement is correct?
partial orders
Medium
A. is the greatest element.
B. is the least element.
C. is the unique minimal element.
D. is the unique minimal element.
Correct Answer: is the greatest element.
Explanation:
Every element of divides , so is the greatest element. Both and are minimal, and there is no least element.
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36In the poset , what is the least upper bound of and ?
partial orders
Medium
A.
B.
C.
D.
Correct Answer:
Explanation:
Under inclusion, the least upper bound is the union. Here .
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37In the lattice of positive divisors of ordered by divisibility, what are the meet and join of and , respectively?
lattices
Medium
A. and
B. and
C. and
D. and
Correct Answer: and
Explanation:
In a divisibility lattice, the meet is the greatest common divisor and the join is the least common multiple. Thus and .
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38In the lattice , which operations represent meet, join, and complement?
lattices
Medium
A.Intersection, difference, and union
B.Union, intersection, and set difference
C.Difference, union, and intersection
D.Intersection, union, and relative complement
Correct Answer: Intersection, union, and relative complement
Explanation:
For a power-set lattice, meet is intersection, join is union, and the complement of is .
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39In the additive group , what is the order of the element ?
groups
Medium
A.
B.
C.
D.
Correct Answer:
Explanation:
The order of in is . Indeed, .
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40Let and in . Using right-to-left composition, what is ?
groups
Medium
A.
B.
C.
D.
Correct Answer:
Explanation:
Apply first and then : , , and is fixed. Hence the product is .
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41How many truth assignments satisfy the formula ?
propositional logic
Hard
A.
B.
C.
D.
Correct Answer:
Explanation:
If is false, the first implication forces . If is true, the second forces . Thus exactly two assignments satisfy the formula.
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42From the premises , , and , which conclusion is logically necessary?
propositional logic
Hard
A.
B.
C.
D.
Correct Answer:
Explanation:
The first two premises imply . If were true, then would be true, contradicting . Hence follows.
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43Which set of connectives is functionally complete, meaning that every Boolean function can be expressed using only connectives from that set?
propositional logic
Hard
A.
B.
C.
D.
Correct Answer:
Explanation:
Using implication and falsehood, can be written as , and as . Since and are functionally complete, so is .
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44Let mean " is strictly greater than ." Which formula states that every element has a strictly greater element, while no element is strictly greater than itself?
first order logic
Hard
A.
B.
C.
D.
Correct Answer:
Explanation:
The first conjunct gives each some strictly greater . The second enforces irreflexivity by excluding for every element.
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45Consider the sentence Over structures with a nonempty domain, which statement is correct?
first order logic
Hard
A.It has both finite and infinite models.
B.It has infinite models but no finite models.
C.It has finite models but no infinite models.
D.It has no models of any cardinality.
Correct Answer: It has infinite models but no finite models.
Explanation:
The sentence says that is injective but not surjective. On a finite set every injective self-map is surjective, while infinite sets such as admit injective nonsurjective maps.
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46Assuming nonempty domains, which formula is logically equivalent to ?
first order logic
Hard
A.
B.
C.
D.
Correct Answer:
Explanation:
Move the negation through the quantifiers and use . Also, is equivalent to .
Incorrect! Try again.
47Let be countably infinite, and let be the set of all finite subsets of . What is the cardinality of ?
sets
Hard
A.
B.
C.
D.
Correct Answer:
Explanation:
is countable, while has cardinality . Therefore .
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48For finite sets , suppose , , , , , , and . How many elements belong to exactly one of the three sets?
sets
Hard
A.
B.
C.
D.
Correct Answer:
Explanation:
The number in exactly one set is .
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49Define a relation on by if and only if or . Which description of is correct?
relations
Hard
A.It is symmetric and transitive but not reflexive.
B.It is an equivalence relation with six classes.
C.It is an equivalence relation with four classes.
D.It is reflexive and symmetric but not transitive.
Correct Answer: It is an equivalence relation with four classes.
Explanation:
The condition is , which is an equivalence relation. Its residue classes up to sign are , , , and .
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50On , let . How many ordered pairs are in the transitive closure , where paths must have positive length?
relations
Hard
A.
B.
C.
D.
Correct Answer:
Explanation:
The elements form a directed cycle, so each reaches all three, producing nine pairs. Each also reaches , producing three more pairs. Element reaches nothing.
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51How many surjective functions exist from a -element set onto a -element set?
functions
Hard
A.
B.
C.
D.
Correct Answer:
Explanation:
By inclusion-exclusion, the count is .
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52Let and satisfy . Which conclusion must hold?
functions
Hard
A. is necessarily .
B. is surjective and is injective.
C. is injective and is surjective.
D.Both and are necessarily bijective.
Correct Answer: is injective and is surjective.
Explanation:
A left inverse makes injective: implies . Every equals , so is surjective.
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53Consider the positive divisors of ordered by divisibility. How many maximal chains run from to ?
partial orders
Hard
A.
B.
C.
D.
Correct Answer:
Explanation:
Since , a maximal chain increases one prime exponent at each step. The five increases can be ordered in ways.
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54A poset on has only the nontrivial constraints , , , and , with incomparable to every other element. How many linear extensions does it have?
partial orders
Hard
A.
B.
C.
D.
Correct Answer:
Explanation:
On , the only extensions are and . For each, can be inserted into any of five positions, giving .
Incorrect! Try again.
55What is the maximum possible size of an antichain in the Boolean poset ?
partial orders
Hard
A.
B.
C.
D.
Correct Answer:
Explanation:
By Sperner's theorem, the largest antichain is a largest rank level. The level of all -element subsets has size .
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56In the lattice of positive divisors of ordered by divisibility, with meet and join , how many elements have a complement?
lattices
Hard
A.
B.
C.
D.
Correct Answer:
Explanation:
A complement pair must have gcd and lcm . Each complete prime-power factor must be assigned to exactly one member of the pair, giving complemented divisors.
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57Which combination of properties correctly describes the five-element diamond lattice ?
lattices
Hard
A.Modular, distributive, and uncomplemented
B.Nonmodular, complemented, and distributive
C.Modular, complemented, and nondistributive
D.Distributive, complemented, and nonmodular
Correct Answer: Modular, complemented, and nondistributive
Explanation:
is the standard minimal example of a nondistributive modular lattice. Each of its three atoms is complemented by either of the other two atoms.
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58How many group homomorphisms have an image of order exactly ?
groups
Hard
A.
B.
C.
D.
Correct Answer:
Explanation:
A homomorphism is determined by the image of . Its image has order exactly when has order in . There are such elements.
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59How many permutations satisfy ?
groups
Hard
A.
B.
C.
D.
Correct Answer:
Explanation:
Such permutations consist only of -cycles and -cycles. They are the identity, the six transpositions, and the three products of two disjoint transpositions, totaling .
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60Let be a nonabelian group of order . How many elements of order does contain?
groups
Hard
A.
B.
C.
D.
Correct Answer:
Explanation:
The number of Sylow -subgroups divides and satisfies , so it is or . If it were , both Sylow subgroups would be normal and would be cyclic. Thus , giving elements of order .
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