Page 108 - ICSE Math 6

2. If A is a set of the first seven multiples of 5, then fill in the blanks with ∈ or ∉.

(a) 1 ____ A (b) 10 ____ A (c) 50 ____ A (d) 25 ____ A
3. Write True or False.
(a) If A = {1, 3, 4, 5}, then n(A) = 5.

(b) If X = {x | x ∈ W}, then 1 ∈ X.
(c) If B = {x | –3 ≤ x ≤ 5}, then –4 ∈ B.
(d) If Y = {x | x + 5 = 0, x ∈ Z}, then –5 ∈ Y.

(e) The set of odd prime numbers is a finite set.
4. Write down the elements of set X if:
(a) it consists of vowels used in the word KOLKATA.

(b) it contains natural numbers between 20 and 30, divisible by 5.
(c) it consists of even prime numbers less than 25.
(d) it is a set of first six multiples of 8.

5. State whether the following sets are finite or infinite.
(a) {11, 22, 33, …}

(b) X = {x | x is a prime number}
(c) {10, 20, 30, …, 100}
(d) B = {x | x is a multiple of 6}
(e) A = {x | x is an even number less than 100}

(f) Y = {x | x is a decimal number between 1 and 2}

PRACTICE TIME

1. Write the following sets in the roster form.

(a) The set M of all the months in a year.
(b) The set D of all the proper divisors of 40.

(c) The set P of 2-digit prime numbers less than 50.
(d) The set A of all the vowels of the word GEOMETRY.

(e) A = {x | 7x + 7 = 14, x ∈ Z}
(f) B = {x | x = 5n, n ∈ N and n ≤ 5}

2. Write the following sets in the set-builder form.
(a) A = {2, 4, 6, …} (b) X = {Spring, Summer, Autumn, Winter}

 1 1 1 1
(c) B = 1,, ,,  (d) D = {a, b, c, d, e, f}

 23 45
3. If A = {10, 20, 30, 40, 50}, write the roster form of set B whose members are obtained by
subtracting 6 from the members of set A. Also, complete the set-builder form of set B given by
B = {y | y = x + ( ____ ), x ∈ ____ }.

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