Q4 of 43 Page 6

Write with reasons, which of the following sets are finite or infinite. We know that if a set is a null set or number of elements are limited and countable then it is called ‘Finite set’ and if number of elements in a set is unlimited and uncountable then the set is called ‘Infinite set’.

i. A = {x|x < 10, x is a natural number}


ii. B = {y |y< -1, is an integer}


iii. C = Set of students of class 9 from your school.


iv. Set of people from your village.


v. Set of apparatus in laboratory


vi. Set of whole numbers


vii. Set of rational number

i. A = {x|x < 10, x is a natural number}


∴ A = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}


Ans. A is a finite set.


ii. B = {y |y< -1, y is an integer}


∴ B = {… -5, -4, -3, -2}


Ans. B is an infinite set.


iii. C = {a, b, c, d, e, …}


Ans. C is an infinite set.


iv. D = {Sarpanch, villager1, villager2, …}


Ans. D is an infinite set.


v. E = {Beakers, funnels, chemicals, thermometers, …}


Ans. E is an infinite set.


vi. W = {1, 2, 3, 4, 5, …}


Ans. W is an infinite set.


vii. Q = {(p/q) |p, q ∈ I, q ≠ 0}


Q = {1/2, 1/3, 1/4, …}


Ans. Q is an infinite set.


More from this chapter

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2

Decide whether set A and B are equal sets. Give reason for your answer.

A = Even prime numbers


B = {x| 7x – 1 = 13}

 3

Which of the following are empty sets? Why?

i. A = {a |a is a natural number smaller than zero.}


ii. B = {x|x2 = 0}


iii. C = {x|5x – 2 = 0, x ∈ N}

 1

If A = {a, b, c, d, e}, B = {c, d, e, f}, C = {b, d} and D = {a, e}.

then which of the following statements are true and which are false?


i. C ⊆ B ii. A ⊆ D
iii. D ⊆ B iv. D ⊆ A


v. B ⊆ A vi. C ⊆ A

 2

Take the set of natural numbers from 1 to 20 as universal set and show set X and Y using Venn diagram.

i. X = {x | x ∈ ℕ, and 7 < x < 15}


ii. Y = {y | y ∈ ℕ, y is prime number from 1 to 20}