**NCERT Solutions for Class 11 Maths Chapter 1 Sets Ex 1.2**

NCERT Solutions for Class
11 Maths Chapter 1 Sets Ex 1.2 are the part of NCERT Solutions for Class 11
Maths. Here you can find the NCERT Solutions for Class 11 Maths Chapter 1 Sets
Ex 1.2.

**Ex 1.2 Class 11 Maths Question 1.**

Which of the following are examples of the null set?**(i)**Set of odd natural numbers divisible by 2

**(ii)**Set of even prime numbers

**(iii)**{x: x is a natural number, x < 5 and x > 7}

**(iv)**{y: y is a point common to any two parallel lines}

**Solution.**

**(i)** The set of odd natural numbers divisible by 2 is a null set
because odd natural numbers are not divisible by 2.

**(ii)** The set of even prime numbers is {2} which is not a null set.

**(iii)** {x: x is a natural number, x < 5 and x >7} is a null
set because there is no natural number which satisfies x < 5 and x > 7
simultaneously.

**(iv)** {y: y is a point common to any two parallel lines} is a null
set because two parallel lines do not have any common point.

**Ex 1.2 Class 11
Maths Question 2.**

Which
of the following sets are finite or infinite?**The set of months of a year**

**(i)****(ii)**{1, 2, 3, …}

**(iii)**{1, 2, 3, …, 99, 100}

**(iv)**The set of positive integers greater than 100

**(v)**The set of prime numbers less than 99

**Solution.**

**(i)** The
set of months of a year is finite set because there are 12 months in a year.

**(ii)** {1,
2, 3, …} is an infinite set because there are infinite number of elements in
the set.

**(iii)** {1,
2, 3, …, 99, 100) is a finite set because the set contains finite number of
elements.

**(iv)** The
set of positive integers greater than 100 is an infinite set because there are
infinite number of positive integers greater than 100.

**(v)** The
set of prime numbers less than 99 is a finite set because the set contains
finite number of elements.

**Ex 1.2 Class 11
Maths Question 3.**

State
whether each of the following set is finite or infinite:**The set of lines which are parallel to the x-axis**

**(i)****(ii)**The set of letters in the English alphabet

**(iii)**The set of numbers which are multiple of 5

**(iv)**The set of animals living on the earth

**(v)**The set of circles passing through the origin (0, 0)

**Solution.**

**(i)** The
set of lines which are parallel to the x-axis is an infinite set because we can
draw infinite number of lines parallel to x-axis.

**(ii)** The
set of letters in the English alphabet is a finite set because there are 26
letters in the English alphabet.

**(iii)** The
set of numbers which are multiple of 5 is an infinite set because there are
infinite number of multiples of 5, i.e., 5, 10, 15, 20, …….

**(iv)** The
set of animals living on the earth is a finite set because the number of
animals living on the earth is very large but finite.

**(v)** The
set of circles passing through the origin (0, 0) is an infinite set because we
can draw infinite number of circles passing through origin with different
radii.

**Ex 1.2 Class 11
Maths Question 4.**

In
the following, state whether A = B or not:**A = {a, b, c, d}; B = {d, c, b, a}**

**(i)****(ii)**A = {4, 8, 12, 16}; B = {8, 4, 16, 18}

**(iii)**A = {2, 4, 6, 8, 10}; B = {x: x is positive even integer and x ≤ 10}

**(iv)**A = {x: x is a multiple of 10}; B = {10, 15, 20, 25, 30, …}

**Solution.**

**(i)** A
= {a, b, c, d} and B = {d, c, b, a} are equal sets because order of elements
does not change a set.

∴ A = B = {a, b, c, d}

**(ii)** A = {4, 8, 12, 16} and B = {8, 4,
16, 18} are not equal sets because 12 ∈ A but 12 ∉ B and 18 ∈ B but 18 ∉ A.

**(iii)** A = {2, 4, 6, 8, 10} and B = {x: x
is a positive even integer and x ≤ 10) which can be written in roster form as B
= (2, 4, 6, 8, 10) are equal sets.

∴ A = B = {2, 4, 6, 8, 10}

**(iv)** A = {x: x is a multiple of 10) can
be written in roster form as A = {10, 20, 30, 40, ……..} and B = {10, 15, 20,
25, 30, ………..} are not equal sets because 15 ∈ B but 15 ∉ A.

**Ex 1.2 Class 11
Maths Question 5.**

Are
the following pairs of sets equal? Give reasons.**A = {2, 3}; B = {x: x is solution of x**

**(i)**^{2}+ 5x + 6 = 0}

**(ii)**A = {x: x is a letter in the word FOLLOW}; B = {y: y is a letter in the word WOLF}

**Solution.**

**(i)** A
= (2, 3} and B = {x: x is a solution of x^{2} + 5x + 6 = 0}

Now, x^{2} + 5x + 6 = 0 ⇒ x^{2} + 3x + 2x + 6 = 0

⇒ (x + 3)(x + 2) = 0

⇒ x = -3, -2

∴ B = {-2, -3}

Hence, A and B are not equal sets.

**(ii)** A = {x: x is a letter in the word
FOLLOW} = {F, O, L, W}

B = {y: y is a letter in the word WOLF} = {W, O, L, F}

Hence, A = B = {F, O, L, W}

**Ex 1.2 Class 11
Maths Question 6**

From
the sets given below, select equal sets:**A = {2, 4, 8, 12),**

B = {1, 2, 3, 4},

C = {4, 8, 12, 14},

D = {3, 1, 4, 2},

E = {-1, 1},

F = {0, a},

G = {1, -1},

H = {0, 1}

**Solution.**

From the given sets, we see that sets B and D have the same elements and also
sets E and G have the same elements.

∴ B = D = {1 ,2, 3, 4} and E = G = {-1,
1}.

**You can also like these:**

**NCERT Solutions for Maths Class 9**

**NCERT Solutions for Maths Class 10**