1. Which of the following are sets? Justify your answer.

(i) The collection of all the moments of a year beginning with the letter J.

Yes, Because it contain particular answer.

(ii) The collection of ten not talented writers in India.

No, Because it does not contain particular answer.

(iii) A team of eleven cricket batsmen of the world.

No, it does not contain well-defined answer.

(iv) The collection of all the boys in your class.

Yes, it contain well-defined answer.

(v) The collection of all natural no. less than 100.

Yes, it has a particular answer.

(vi) A collection of novels written by the written Munshi pram chand.

  Yes, it has a well-defined answer.

(vii) The collection of even integers.

Yes, it has a particular answer.

(viii) The collection of questions in this chapter.

Yes, it has a well-defined answer.

(ix) A collection of most dangerous animals of the world.

No, it does not contain well-defined answer.

2. let A = {1, 2, 3, 4, 5, 6}. Insert the appropriate symbol {or Є or ∉ in the blank species:

(i) 5…Є…A    (i) 8…∉…A (i) O…∉…A

(iv) 4…Є…A  (v) 2…Є…A               (vi) 10…∉…A

3. Write the following sets in roster form:-

(i) A = {x:x is an integer and -3 < x < 7}

A = {-2, -1, 0, 1, 2, 3, 4, 5, 6}

(iii) B = {x:x is a two-digit natural no. less than 6}

B = {1, 2, 3, 4, 5}

(iii) C = {x:x is a two-digit natural no. such that the sum of its digits is 8}

C = {17, 26, 35, 44, 53, 62, 71, 80}

(iv) D {x:x is a prime no. which is divisor of 60}

D = {2, 3, 5}

(v) E = The set of all letters in the word BETTER.

E = {B, E, T, R}

(vi) F = The set of all letters in the word TRIGNOMETRY.

F = {TRIGONMEY}.

4. Write the following sets in set-builder form:-

(i) {3, 6, 9, 12}

Let A = {3, 6, 9, 12}.

A = {3X1, 3X2, 3X3, 3X4}

Therefore A = {x : x = 3n, n Є N, 1 ≤ n ≤ 4}

(ii) {2, 4, 8, 16, 32}

Let B = {2, 4, 8, 16, 32}

B = {2¹, 2², 2³, 2⁴, 2⁵}

Therefore B = {x:x = 2ⁿ, n Є N, 1 ≤ x ≤ 5}

(iii) {5, 25, 125, 625}

Let C = {5, 25, 125, 625}

C = {5¹, 5², 5³, 5⁴}

Therefore

C = {x:x = 5ⁿ , n Є N, 1 ≤ x ≤ 4}

(iv) {2, 4, 6}

Let D = {2, 4, 6}

D = {2X1, 2X2, 2X3}

Therefore

D = {x:x is an even natural number}

(v) {1, 4, 9, ….., 10}

Let E = { 1, 4, 9, ……,100}

E = {1², 2², 3², …. 10²}

Therefore

E = {x:x = n², n Є N, 1 ≤ n ≤ 10}

5. List all the elements of all the sets:-

(i) A = {x:x is an odd natural no.}.

A = {1, 3, 5, 7, 9, .…..}.

B = {0, 1, 2, 3, 4}

(iii) C = {x:x is an integer, x² ≤ 4}.

C = {-2, -1, 0, 1, 2, 3,}.

(iv) D = {x:x is a letter in the word “LOYAL”}.

D = {L, O, Y, A}.

(v) E = {x:x is a month of a year not having 31 days}.

E = {February, April, June, September, November}

(vi) F = {x:x is a consonant in the English alphabet which precedes R}

F = { b, c, d, j, g, h, j}.