Tag: mathematical reasoning

Questions Related to mathematical reasoning

"If it is a good watch then it is a Titan watch. It is a Titan watch, therefore, it is a good watch". This argument is _____________.

  1. valid

  2. invalid

  3. may be valid or invalid

  4. invalid if conditional connective is replaced by biconditional connective


Correct Option: A

While simplifying $\sqrt { \frac { 1-cosx }{ 1+cosx }  } $, two students got the following two answers A & B.
A)  cosec x - cot x  (B)   $\frac { 1 }{ cosecx+cotx } $ What can you say about answers ?

  1. Both A & B are worng

  2. Both A & B are right

  3. A is right B is wrong

  4. B is right A is wrong


Correct Option: A
State whether the statement
P: "if x is a real number such that $x^3+2x=0$, then $x$ is $0$"  is true/false
  1. True

  2. False


Correct Option: A

State whether the statement
P: "if x is a real number such that $x^3+2x=0$, then $x$ is $0$" is true/false.

  1. True

  2. False


Correct Option: A

Choose the incorrect statements

  1. Digit at the units place of $3^{51}$ is $9$

  2. If $i-f=(9-\sqrt{82})^{11}$ and $< f < 1 $, then $'i'$ is an even integers

  3. If $7^{80}$ is divided by $13$, then the remainder is $9$

  4. If only $6^{th}$ term in the expression of $\left(\dfrac{x}{5}+\dfrac{2}{5}\right)^{n} $ ahs numerically greatest coefficient, then $n=7$


Correct Option: A

Check the validity of the following statement:
$p:100$ is a multiple of $4$ and $5$

  1. True

  2. False


Correct Option: A
Explanation:

$r:100$ is a multiple of $4\rightarrow$ TRUE $(4\times 25)$


$s:100$ is a multiple of $5\rightarrow$ TRUE $(5\times 20)$

Hence $p$ is true

Determine whether the argument used to check the validity of the following statement is correct.
$p:$ If $x^{2}$ is irrational, then $x$ is rational'
The statement is true because the number $x^{2}=\pi^{2}$ is irrational, therefore $x=\pi$ irrational.

  1. True

  2. False


Correct Option: B
Explanation:

Here, the argument used is,


$x^2=\pi^2$ is irrational, therefore $x=\pi$ is irrational and, $p:$ " If 

$x^2$ is irrational, then $x$ is rational.

Let us take an irrational number given by $x=\sqrt n$,
where $n$ is a rational number.

Now, square both sides, we get,
$x^2=k$

Therefore, $x^2$ is a rational number, which contradicts our statement. 
Hence, the argument used to check validity of given statement is false.

Check the validity of the following statement:
$p:60$ is a multiple of $3$ and $5$

  1. True

  2. False


Correct Option: A
Explanation:
$r:60$ is a multiple of $3\quad (3\times 20)$

$s:60$ is a multiple of $5\quad (5\times 12)$

Hence $p$ is true

State whether the statement
$p:$ If $x$ is a real number such that $x^{3}+19x=0$ , then $x$ is $0$ is true / False

  1. True

  2. False


Correct Option: A
Explanation:

$x^3 + 19x= 0$

$x(x^2 + 19)=0$
$x = 0$,      $x^2 + 19 =0$ 
so given statement is true

Check the validity of the following statement:
$p:125$ is a multiple of $5$ and $7$

  1. True

  2. False


Correct Option: B
Explanation:
$r:125$ is a multiple of $5\rightarrow$ TRUE $(5\times 25)$

$s:125$ is a multiple of $7\rightarrow$ FALSE 

Hence $p$ is false.