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SETS

**Class 11 - Mathematics **

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NCERT Exercise 1.1

**Question 1: Which of the following are sets? Justify your answer.**
(i) The collection of all months of a year beginning with the letter J.

(ii) The collection of ten most talented writers of India.

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

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

(v) The collection of all natural numbers less than 100.

(vi) A collection of novels written by the writer Munshi Prem Chand.

(vii) The collection of all even integers.

(viii) The collection of questions in this Chapter.

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

Answer:

**(i)** Yes

The collection of all months of a year beginning with the letter J is a well-defined collection of objects since one can definitely identify a month that belongs to this collection. Hence, this collection is a set.

**(ii)** No

The collection of ten most talented writers of India is not a well-defined collection because the criteria for determining a writer’s talent may vary from person to person. Hence, this collection is not a set.

**(iii)** No

A team of eleven best cricket batsmen of the world is not a well-defined collection because the criteria for determining a batsman’s talent may vary from person to person. Hence, this collection is not a set.

**(iv)** Yes

The collection of all boys in your class is a well-defined collection because you can definitely identify a boy who belongs to this collection. Hence, this collection is a set.

**(v)** Yes

The collection of all natural numbers less than 100 is a well-defined collection because one can definitely identify a number that belongs to this collection. Hence, this collection is a set.

**(vi)** Yes

A collection of novels written by the writer Munshi Prem Chand is a well-defined collection because one can definitely identify a book that belongs to this collection. Hence, this collection is a set.

**(vii)** Yes

The collection of all even integers is a well-defined collection because one can definitely identify an even integer that belongs to this collection. Hence, this collection is a set.

**(viii)** Yes

The collection of questions in this chapter is a well-defined collection because one can definitely identify a question that belongs to this chapter. Hence, this collection is a set.

**(ix)** No

The collection of most dangerous animals of the world is not a well-defined collection because the criteria for determining the generousness of an animal can vary from person to person. Hence, this collection is not a set.