Engineering Questions with Answers - Multiple Choice Questions
MCQs on Logics – Nested Quantifiers
1 - Question
Let Q(x, y) denote “M + A = 0.” What is the truth value of the quantifications ∃A∀M Q(M, A).
a) True
b) False
View Answer
Answer: b
Explanation: For each A there exist only one M, because there is no real number A such that M + A = 0 for all real numbers M.
2 - Question
Translate ∀x∃y(x < y) in English, considering domain as a real number for both the variable.
a) For all real number x there exists a real number y such that x is less than y
b) For every real number y there exists a real number x such that x is less than y
c) For some real number x there exists a real number y such that x is less than y
d) For each and every real number x and y such that x is less than y
View Answer
Answer: a
Explanation: Statement is x is less than y. Quantifier used are for each x, there exists a y.
3 - Question
“The product of two negative real numbers is not negative.” Is given by?
a) ∃x ∀y ((x < 0) ∧ (y < 0) → (xy > 0))
b) ∃x ∃y ((x < 0) ∧ (y < 0) ∧ (xy > 0))
c) ∀x ∃y ((x < 0) ∧ (y < 0) ∧ (xy > 0))
d) ∀x ∀y ((x < 0) ∧ (y < 0) → (xy > 0))
View Answer
Answer: d
Explanation: For every negative real number x and y, the product of these integer is positive.
4 - Question
. Let Q(x, y) be the statement “x + y = x − y.” If the domain for both variables consists of all integers, what is the truth value of ∃xQ(x, 4).
a) True
b) False
View Answer
Answer: b
Explanation: There exist no integer for which x+4=x-4.
5 - Question
Let L(x, y) be the statement “x loves y,” where the domain for both x and y consists of all people in the world. Use quantifiers to express, “Joy is loved by everyone.”
a) ∀x L(x, Joy)
b) ∀y L(Joy,y)
c) ∃y∀x L(x, y)
d) ∃x ¬L(Joy, x)
View Answer
Answer: a
Explanation: Joy is loved by all the people in the world.
6 - Question
. Let T (x, y) mean that student x likes dish y, where the domain for x consists of all students at your school and the domain for y consists of all dishes. Express ¬T (Amit, South Indian) by a simple English sentence.
a) All students does not like South Indian dishes.
b) Amit does not like South Indian people.
c) Amit does not like South Indian dishes.
d) Amit does not like some dishes.
View Answer
Answer: d
Explanation: Negation of the statement Amit like South Indian dishes.
7 - Question
Express, “The difference of a real number and itself is zero” using required operators.
a) ∀x(x − x! = 0)
b) ∀x(x − x = 0)
c) ∀x∀y(x − y = 0)
d) ∃x(x − x = 0)
View Answer
Answer: b
Explanation: For every real number x, difference with itself is always zero.
8 - Question
. Use quantifiers and predicates with more than one variable to express, “There is a pupil in this lecture who has taken at least one course in Discrete Maths.”
a) ∃x∃yP (x, y), where P (x, y) is “x has taken y,” the domain for x consists of all pupil in this class, and the domain for y consists of all Discrete Maths lectures
b) ∃x∃yP (x, y), where P (x, y) is “x has taken y,” the domain for x consists of all Discrete Maths lectures, and the domain for y consists of all pupil in this class
c) ∀x∀yP(x, y), where P (x, y) is “x has taken y,” the domain for x consists of all pupil in this class, and the domain for y consists of all Discrete Maths lectures
d) ∃x∀yP(x, y), where P (x, y) is “x has taken y,” the domain for x consists of all pupil in this class, and the domain for y consists of all Discrete Maths lectures
View Answer
Answer: a
Explanation: For some x pupil, there exists a course in Discrete Maths such that x has taken y.
9 - Question
Determine the truth value of ∃n∃m(n + m = 5 ∧ n − m = 2) if the domain for all variables consists of all integers.
a) True
b) False
View Answer
Answer: b
Explanation: The equation does not satisfy any value of m and n in the domain consist of integers.
10 - Question
Find a counterexample of ∀x∀y(xy > y), where the domain for all variables consists of all integers.
a) x = -1, y = 17
b) x = -2 y = 8
c) Both x = -1, y = 17 and x = -2 y = 8
d) Does not have any counter example
View Answer
Answer: c
Explanation: Putting x=-1, y=17; -17>17 which is wrong. Putting x=-2, y=8; -16>8 which is wrong.