viii The collection of questions in this Chapter. ix A collection of most dangerous animals of the world. Answer i 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. ii 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 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 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 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 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 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 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 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.

Question 2 Let A 1, 2, 3, 4, 5, 6 . Insert the appropriate symbol or in the blank spaces i 5 A ii 8 A iii 0 A iv 4 A v 2 A vi 10 A Answer i 5 A ii 8 A iii 0 A iv 4 A v 2 A vi 10 A

Question 3 Write the following sets in roster form i A x x is an integer and 3 x 7 . ii B x x is a natural number less than 6 . iii C x x is a two-digit natural number such that the sum of its digits is 8