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11th Grade > Mathematics

MATHEMATICAL REASONING MCQs

Total Questions : 30 | Page 2 of 3 pages
Question 11.


Let p,q, and r be any three logical statements. Which of the following is true?


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

Only option C is correct. It is a direct application of Demorgan's law.
(p q)=p (q)=p q


Question 12.


Two statements p and q are given below.


p: 2 plus 3 is 5
q: Delhi is the capital of India


Then the statement "Delhi is the capital of India and it is not that 2 plus 3 is five" is


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

p: 2 plus 3 is 5
q: Delhi is the capital of India
~p: it is not that 2 plus 3 is five.
Then the given statement is q p or p  q


Question 13.


Two statements p and q are given below


p: It is snowing
q: I am cold


The compound statement "It is snowing and it is not that I am cold" is given by


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

p: It is snowing
q: I am cold
~q: It is not that I am cold


Then the given statement is p q


Question 14.


Which one of the following is not a logical statement?


  1.     5 is a composite number
  2.     London is the capital of England
  3.     You are a boy
  4.     The sun is a star
 Discuss Question
Answer: Option C. -> You are a boy
:
C

A logical statement is a statement which has a definite truth value which is invariant. Here the statement 'you are a boy' depends on who 'you' are. Hence, it is not invariant.


Question 15.


If S(p,q,r)=p (q  r) is a compund statement, then S(~p,~q,~r) is


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

S(p,q,r)=p (q  r)S( p, q, r)=(p) (q r)=p ((q  r))=p (q  r)


Question 16.


Let p: Roses are red and q: The sun is a star. Then the verbal translation of p  q is


  1.     Roses are not red and the sun is not a star
  2.     It is not true that roses are red or the sun is not a star
  3.     Roses are not red and the sun is a star
  4.     Roses are not red or the sun is a star
 Discuss Question
Answer: Option D. -> Roses are not red or the sun is a star
:
D

p: Roses are red
q: The sun is a star
~p: Roses are not red
p  q: Roses are not red or the sun is a star


Question 17.


Negation of "2+3 =5 and 8  is less than 10 " is 


  1.     2+35 and 8 is less than 10
  2.     2+35 or 8 is less than 10
  3.     2+35 and 8 is not less than 10
  4.     2+35 or 8 is not less than 10
 Discuss Question
Answer: Option D. -> 2+35 or 8 is not less than 10
:
D

p: 2+3 =5
q: 8 is less than 10
 p  q=p q
p q:2+35 or 8 is not less than 10


Question 18.


Which of the following is not a statement?


  1.     All roses are red
  2.     Kerala is in India
  3.     Every rectangle is a square
  4.     I have failed
 Discuss Question
Answer: Option D. -> I have failed
:
D

The sentence I have failed can have different truth values depending on context. Hence, it is not a statement. Options A and D are false and option B is true.


Question 19.


All prime numbers are odd. State true or false.


  1.     True
  2.     False
  3.     Mathematics is fun
  4.     Earth is a planet
 Discuss Question
Answer: Option B. -> False
:
B

The statement can be proved false if we can find a counterexample to the given statement. 2 is a prime number which is even. Hence, the statement is false.


Question 20.


Select the statement(s) from the given sentences.


  1.     8 is less than 6
  2.     Every set is a finite set
  3.     Mathematics is fun
  4.     Earth is a planet
 Discuss Question
Answer: Option B. -> Every set is a finite set
:
A, B, and D

A logical statement is a statement which has a definite truth value which is invariant. Here, options A, B and D have definite truth values. Option C may be true or false for different people.


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