1.Which of the following are sets? Justify your answer.
(i) The collection of all the months of a year beginning with the letter J.
The collection of all months of a year beginning with J is {January, June, July}, which is well defined and hence it forms a set.
(ii) The collection of ten most talented writers of India.
The collection of most talented writers of India is not well defined because opinions about ‘most talented writers’ vary from person to person and hence it does not form a set.
(iii) A team of eleven best-Cricket batsmen of the world.
A team of eleven best-cricket batsmen of the world us not well defined because opinion about ‘best cricket batsmen’ vary from person to person and hence it does not form a set
(iv) The collection of all boys in your class.
The collection of all boys in your class is well defined and hence it forms a set.
(v) The collection of all natural numbers less than 100.
The collection of all natural numbers less than 100 is {1, 2, 3, ......., 99} which is well defined and hence it forms a set.
(vi) A collection of novels written by the writer Munshi Prem Chand.
A collection of novels written by the writer Munshi Prem Chand is well defined and hence it forms a set.
(vii) The collection of all even integers.
The collection of all even integers is { ..........., -4, -2, 0, 2, 4,..........}, which is well defined and hence it forms a set.
(viii) The collection of questions in the chapter.
The collection of questions in this chapter is well defined and hence it forms a set.
(ix) A collection of most dangerous animals of the world.
A collection of most dangerous animals of the world is not well defined because opinion about ‘most dangerous animals’ vary from person to person and hence it does not form a set.
2. Let A = {1, 2, 3, 4, 5, 6}. Insert the appropriate symbol ∈ or ∉ on the blank space:
(i) 5 ∈ A. (ii) 8 ∉ A. (iii) 0 ∉ A. (iv) 4 ∈ A. (v) 2 ∈ A. (vi) 10 ∉ A.
3. Write the following sets in roster form:
(i) A = {x : x is an integer and -3
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