Page 106 - ICSE Math 6

(d) All the easy problems of your textbook.
(e) All the wise ladies of your city.

2. Write True or False.
(a) Sets {a, e, i, o, u} and {u, e, o, i, a} are not the same.
(b) Sets {1, 0, 5, 9, 13} and {1, 5, 9, 13} are the same.
(c) If B is a set of letters in the word ‘STATISTICS’, then B = {S, T, A, I, C}.
(d) A set of first four prime numbers in set-builder form is given by {2, 3, 5, 7}.

3. Let X be the set of letters of the word ‘ANDHRA PRADESH’. Fill in the blanks with ‘∈’ or ‘∉’.
(a) T ___ X (b) P ___ X (c) S ___ X (d) M ___ X
4. Write the following sets in the roster form.
(a) The set X of first five multiples of 6.
(b) The set A of whole numbers less than 25 which are multiples of 4.
(c) The set P of prime numbers between 15 and 30.
(d) The set B of the letters of the word ‘INFINITE’.

5. Write the following sets in the set-builder form.
(a) A = {–1, –2, –3, –4, –5, –6} (b) B = {7, 14, 21, 28, 35, 42}
(c) X = {2, 3, 5, 7} (d) Y = {Saturday, Sunday}
6. If A = {x | x is even number less than 20}, fill in the blanks with ‘∈’ or ‘∉’.
(a) 12 ___ A (b) 7 ___ A (c) 22 ___ A (d) 0 ___ A

Types of Sets

Finite sets
A set is known as a finite set if it has a finite number of elements, i.e., the elements of the set can be
counted. For example,
(a) {5, 10, 15, 20, 25} is a finite set as it has 5 elements.

(b) {x | x is a whole number greater than 9 and less than 14} is a finite set as it has 4 elements namely,
10, 11, 12 and 13.

Infinite sets
A set is known as an infinite set if it has an infinite number of elements, i.e., the elements of the set
cannot be counted. For example,
(a) The set of natural numbers given by N = {1, 2, 3, …} is an infinite set.

(b) {x | x is a prime number} is an infinite set as there are infinite prime numbers.

Empty sets
A set which has no element is called an empty set or a Try These
null set. It is denoted by { } or by the Greek letter f (read
as phi). For example, 1. Write any two finite sets in set-builder form.
2. Write any two infinite sets in roaster form.
(a) {x | x < 0, x ∈ W} is an empty set as there is no whole 3. Consider the set A = {x : x + 2 ____ 3, x ∈ N}.
number which is less than zero. Fill in the blank with the sign, <, > or =, to
make the set:
(b) {x | 3x = 7, x ∈ Z} is an empty set as there is no (i) finite (ii) infinite (iii) empty
integer which on multiplication with 3 gives 7 as the
product.

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