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11th Grade > Mathematics

MATHEMATICAL REASONING MCQs

Total Questions : 30 | Page 3 of 3 pages
Question 21.


Let p,q,r be three statements. Then (p (q  r)) is equal to


  1.     (p q)  (p r)
  2.     (p q)  (p r)
  3.     (p q)  (p r)
  4.     (p q)  (p r)
 Discuss Question
Answer: Option C. -> (p q)  (p r)
:
C

(p (q  r))=p (q  r)=p  (q r)=(p q)  (p r)


Question 22.


From the given options, the truth values of p,q and r respectively for which (p  q)  (r) has a truth value F are


  1.     F, F, F
  2.     T, T, T
  3.     T, F, F
  4.     F, F, T
 Discuss Question
Answer: Option D. -> F, F, T
:
D

Given that (p  q)  (r) is false.
i) (p  q) is falseii)r is false(p  q) is false
Hence, p and q cannot be true simulaneously.
Also, ~r is false. Hence, r must be true.
Only option D satisfies this condition


Question 23.


Consider the two statements P: He is intelligent and Q: He is strong. Then the symbolic form of the statement "It is not true that he is intelligent or strong" is 


  1.     P  Q
  2.     P Q
  3.     P  Q
  4.     (P  Q)
 Discuss Question
Answer: Option D. -> (P  Q)
:
D

P: He is intelligent
Q: He is strong
 Q: He is intelligent or strong
~( Q): It is not true that he is intelligent or strong


Question 24.


(p  q) is logically equivalent to


  1.     (p  q)
  2.     (p q)
  3.     p q
  4.     p q
 Discuss Question
Answer: Option D. -> p q
:
D

We know that (p  q)= p q


 (p  q)=(p) q=p q


Question 25.


Which of the following is a logical statement?


  1.     Close the door
  2.     Tomorrow is Monday
  3.     Mathematics is interesting
  4.     Paris is the capital of India
 Discuss Question
Answer: Option D. -> Paris is the capital of India
:
D

A logical statement is a statement which has a definite truth value which is invariant. Here, 'Paris is the capital of India' is a statement because we can definitely say that it is false.


Question 26.


Two statements p and q are given below.


p: 7 is not greater than 4
q: Paris is in France


Then the statement (p  q) is


  1.     7 is greater than 4 and Paris is not in France
  2.     7 is greater than 4 or Paris is not in France
  3.     7 is not greater than 4 and Paris is not in France
  4.     7 is not greater than 4 or Paris is not in France
 Discuss Question
Answer: Option A. -> 7 is greater than 4 and Paris is not in France
:
A

p: 7 is not greater than 4
q: Paris is in France
~p: 7 is greater than 4
~q: Paris is not in France
Now, (p  q)=p q


This is the statement '7 is greater than 4 and Paris is not in France'.


Question 27.


Three statements p,q,r are given below


p: 4 is an even prime number
q: 6 is a divisor of 12
r: the HCF of 4 and 6 is 12 


Which of the following are true?


  1.     p (q  r)
  2.     p  q
  3.     (p  q)r
  4.     p(q  r)
 Discuss Question
Answer: Option A. -> p (q  r)
:
A

p: 4 is an even prime number - False
q: 6 is a divisor of 12 - True
r: the HCF of 4 and 6 is 12  - True
It can be seen that the statement p (q  r) is true.


Question 28.


Which of the following is logically equivalent to (pq) ?


  1.     p  q
  2.     p q
  3.     p  q
  4.     p q
 Discuss Question
Answer: Option D. -> p q
:
D

(pq)=p  q(pq)=p  q


Question 29.


Negation of the statement 'if it rains, I shall go to school' is 


  1.     It rains and I shall go to school
  2.     It rains and I shall not go to school
  3.     It does not rain and I shall go to school
  4.     It does not rain and I shall not go to school
 Discuss Question
Answer: Option B. -> It rains and I shall not go to school
:
B

p: It rains
q: I shall go to school
pq: If it rains, I shall go to school
(pq)=p qp q:It rains and I shall not go to school


Question 30.


Find the negation of the statement - 'There exists a rational number x such that its square is 2 '.


  1.     There exists a rational number x such that its square is not 2
  2.     There exists an irrational number x such that its square is 2
  3.     There does not exist a rational number x such that its square is not 2
  4.     There does not exist a rational number x such that its square is 2
 Discuss Question
Answer: Option D. -> There does not exist a rational number x such that its square is 2
:
D

The negation of 'there exists a rational number x such that its square is 2' is 'there does not exist a rational number x such that its square is 2'.


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