ExamGOAL
Books
2
Subjective

Find the component statements of the following compound statements.

(i) Number 7 is prime and odd.

(ii) Chennai is in India and is the capital of Tamil Nadu.

(iii) The number 100 is divisible by 3,11 and 5.

(iv) Chandigarh is the capital of Haryana and UP.

(v) $\sqrt{7}$ is a rational number or an irrational number.

(vi) 0 is less than every positive integer and every negative integer.

(vii) Plants use sunlight, water and carbon dioxide for photosynthesis.

(viii) Two lines in a plane either intersect at one point or they are parallel.

(ix) A rectangle is a quadrilateral or a 5 sided polygon.

Explanation

(i) $p$ : Number 7 is prime.

$q$ : Number 7 is odd.

(ii) P : Chennai is in India.

$q$ : Chennai is capital of Tamil Nadu.

(iii) $p: 100$ is divisible by 3 .

$q$ : 100 is divisible by 11 .

$r: 100$ is divisible by 5 .

(iv) $p$ : Chandigarh is capital of Haryana.

$q$ : Chandigarh is capital of UP.

(v) $p: \sqrt{7}$ is a rational number.

$q: \sqrt{7}$ is an irrational number.

(vi) $p: 0$ is less than every positive integer.

$q: 0$ is less than every negative integer.

(vii) $p$ : Plants use sunlight for photosysthesis.

$q$ : Plants use water for photosynthesis.

$r$ : Plants use carbon dioxide for photosysthesis.

(viii) $p$ : Two lines in a plane intersect at one point.

$q$ : Two lines in a plane are parallel.

(ix) $p$ : A rectangli, is a quadrilateral.

$q$ : A rectangle is a 5 -sided polygon.

3
Subjective

Write the component statements of the following compound statements and check whether the compound statement is true or false.

(i) 57 is divisible by 2 or 3.

(ii) 24 is a multiple of 4 and 6 .

(iii) All living things have two eyes and two legs.

(iv) 2 is an even number and a prime number.

Explanation

(i) Given compound statement is of the form ' $p v q$ '. Since, the statement ' $p v q$ ' has the truth value $T$ whenever either $p$ or $q$ or both have the truth value $T$.

So, it is true statement.

Its component statements are

$p: 57$ is divisible by 2 . [false]

$q: 57$ is divisible by 3 . [true]

(ii) Given compound statement is of the form ' $p \wedge q$ '. Since, the statement ' $p \wedge q$ ' have the truth value $T$ whenever both $p$ and $q$ have the truth value $T$. So, it is a true statement.

Its component statements are

$p: 24$ is multiple of 4 [true]

$q: 24$ is multiple of 6 . [true]

(iii) It is a false statement. Since ' $p \wedge q$ ' has truth value $F$ whenever either $p$ or $q$ or both have the truth value $F$.

Its component statements are

$p$ : All living things have two eyes. [false]

$q$ : All living things have two legs. [false]

(iv) It is a true statement.

Its component statements are

$p: 2$ is an even number. [true]

$q: 2$ is a prime number. [true]

4
Subjective

Write the negative on the following simple statements.

(i) The number 17 is prime.

(ii) $2+7=6$.

(iii) Violets are blue.

(iv) $\sqrt{5}$ is a rational number.

(v) 2 is not a prime number.

(vi) Every real number is an irrational number.

(vii) Cow has four legs.

(viii) A leap year has 366 days.

(ix) All similar triangles are congruent.

(x) Area of a circle is same as the perimeter of the circle.

Explanation

(i) The number 17 is not prime.

(ii) $2+7 \neq 6$.

(iii) Violets are not blue.

(iv) $\sqrt{5}$ is not a rational number.

(v) 2 is a prime number.

(vi) Every real number is not an irrational number.

(vii) Cow has not four legs.

(viii) A leap year has not 366 days.

(ix) There exist similar triangles which are not congruent.

(x) Area of a circle is not same as the perimeter of the circle.

5
Subjective

Translate the following statements into symbolic form

(i) Rahul passed in Hindi and English.

(ii) $x$ and $y$ are even integers.

(iii) 2, 3 and 6 are factors of 12 .

(iv) Either $x$ or $x+1$ is an odd integer.

(v) A number is either divisible by 2 or 3 .

(vi) Either $x=2$ or $x=3$ is a root of $3 x^2-x-10=0$.

(vii) Students can take Hindi or English as an optional paper.

Explanation

(i) $p$ : Rahul passed in Hindi.

$q$ : Rahul passed in English.

$p \wedge q$ : Rahul passed in Hindi and English.

(ii) $p: x$ is even integers.

$q: y$ is even integers.

$p \cap q: x$ and $y$ are even integers.

(iii) $p: 2$ is factor of 12 .

$q: 3$ is factor of 12 .

$r: 6$ is factor of 12 .

$p \wedge q \wedge r: 2,3$ and 6 are factor of 12 .

(iv) $p: x$ is an odd integer.

$q:(x+1)$ is an odd integer.

$p \vee q$ : Either $x$ or $(x+1)$ is an odd integer.

(v) $p$ : A number is divisible by 2 .

$q$ : A number is divisible by 3.

$p \vee q$ : A number is either divisible by 2 or 3 .

(vi) $p: x=2$ is a root of $3 x^2-x-10=0$.

$q: x=3$ is a root of $3 x^2-x-10=0$.

$p \vee q$ : Either $x=2$ or $x=3$ is a root of $3 x^2-x-10=0$.

(vii) $p$ : Students can take Hindi as an optional paper.

$q$ : Students can take English as an optional subject.

$p \vee q$ : Students can take Hindi or English as an optional paper.

6
Subjective

Write down the negation of following compound statements.

(i) All rational numbers are real and complex.

(ii) All real numbers are rationals or irrationals.

(iii) $x=2$ and $x=3$ are roots of the quadratic equation $x^2-5 x+6=0$.

(iv) A triangle has either 3 -sides or 4 -sides.

(v) 35 is a prime number or a composite number.

(vi) All prime integers are either even or odd.

(vii) $|x|$ is equal to either $x$ or $-x$.

(viii) 6 is divisible by 2 and 3 .

Explanation

(i) Let $p$ : All rational numbers are real.

$q$ : All rational numbers are complex.

$\sim p$ : All rational number are not real.

$\sim q$ : All rational numbers are not complex.

$\sim(p \wedge q):$ All rational numbers are not real or not complex. $\quad[\because \sim(p \wedge q)=\sim p \vee \sim q]$

(ii) Let $p$ : All real numbers are rationals.

$q$ : All real numbers are irrational.

Then, the negation of the above statement is given by

$\sim(p \vee q)$ : All real numbers are not rational and all real numbers are not irrational.

$$[\because \sim(p \vee q)=\sim p \wedge \sim q]$$

(iii) Let $p$ : $x=2$ is root of quadratic equation $x^2-5 x+6=0$.

$q: x=3$ is root of quadratic equation $x^2-5 x+6=0$.

Then, the negation of conjunction of above statement is given by

$\sim(p \wedge q): x=2$ is not a root of quadratic equation $x^2-5 x+6=0$ or $x=3$ is not a root of the quadratic equation $x^2-5 x+6=0$.

(iv) Let $p$ : A triangle has 3 -sides.

$q$ : A triangle has 4 -sides.

Then, negation of disjunction of the above statement is given by $\sim(p \vee q)$ : A triangle has neither 3-sides nor 4-sides.

(v) Let $p: 35$ is a prime number.

$q: 35$ is a composite number.

Then, negation of disjunction of the above statement is given by $\sim(p \vee q): 35$ is not a prime number and it is not a composite number.

(vi) Let $p$ : All prime integers are even.

$q$ : All prime integers are odd.

Then negation of disjunction of the above statement is given by

$\sim(p \vee q)$ : All prime integers are not even and all prime integers are not odd.

(vii) Let $p:|x|$ is equal to $x$.

$q:|x|$ is equal to $-x$.

Then negation of disjunction of the above statement is given by

$\sim(p \vee q):|x|$ is not equal to $x$ and it is not equal to $-x$.

(viii) Let $p: 6$ is divisible by 2 .

$q: 6$ is divisible by 3 .

Then, negation of conjunction of above statement is given by

$\sim(p \wedge q): 6$ is not divisible by 2 or it is not divisible by 3