Which of the following are examples of the null set?
(i) Set of odd natural numbers divisible by 2.

(ii) Set of even prime numbers.

(iii) { x : x is a natural number, x < 5 and simultaneously x > 7 }

(iv) { y : y is a point common to any parallel lines }

List all the elements of the following sets:
(i) A = { X:X is an odd natural number }

(ii) B = { X:X is an integer,- < X < }

(iii) C = { X:X is an integer, X²≤ 4 }

(iv) D = { X:X is a letter in the word " LOYAL" }

(v) E = { X:X is a month of a year not having 31 days }

(vi) F = { X:X is a consonant in the english alphabet which precedes k }

Match each of the sets on the left described in the roster form with the
same set on the right described in set builder form:
(i)   {1, 2, 3, 6}               (a) {x: x is a prime number and a divisor of 6}
(ii)  {2, 3}                        (b) {x: x is an odd natural number less than 10}
(iii) {H, A, Y, R, N}           (c) {x: x is a natural number and divisor of 6.}
(iv) {1, 3, 5, 7, 9}            (d) {x: x is a letter of the word 'HARYANA'.}

Which of the following sets is finite or infinite?
(i) The set of the months of a year.
(ii) {1, 2, 3, ……}
(iii) {1, 2, 3, …….., 99, 100}
(iv) The set of positive integers greater than 100.
(v) The set of prime numbers less that 99.

Which of the following sets is finite or infinite?
(i) The set of lines which are parallel to the x-axis.
(ii) The set of letters in the English alphabet.
(iii) The set of numbers which are multiples of 5.
(iv) The set of animals living on earth.
(v) The set of circles in plane passing through the origin(0,0).