Question

Which of the following sets are finite and which are infinite ?
(i) Set of days of a week
(ii) Set of odd positive integers
(iii) Set of irrational numbers between two natural numbers
(iv) Set of prime numbers less than 50.

Answer 1

(i) There are 7 days in a week.
`:.` Set of days of a week is finite set
(ii) Set of odd positive integers `{1,3,5,7…}`, which is infinite
(iii) There are infinite irrational numbers between two natural numbers
`:.` Given set is infinite
(iv) Set of prime numbers less than 50 is `{2,3,5,7,11,13,17,19,23,31,37,41,43,47}` which is finite.