NCERT Solutions
Class 11 Maths
Sets

Ex.1.1 Q.1
Which of the following are sets? Justify your answer.
(1) The collection of all months of a year beginning with the letter J.
(2) The collection of ten most talented writers of India.
(3) A team of eleven best-cricket batsmen of the world.
(4) The collection of all boys in your class.
(5) The collection of all natural numbers less than 100.
(6) A collection of novels written by the writer Munshi Prem Chand.
(7) The collection of all even integers.
(8) The collection of questions in this Chapter.
(9) A collection of most dangerous animals of the world.
(1) The collection of all months of a year beginning with the letter J is a well-defined
collection of objects because one can definitely identify a month that belongs to this collection.
Hence, this collection is a set.
(2) 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.
(3) 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.
(4) 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.
(5) 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.
(6) 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.
(7) 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.
(8) 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.
(9) The collection of most dangerous animals of the world is not a well-defined collection
because the criteria for determining the dangerousness of an animal can vary from person to person.
Hence, this collection is not a set.