Question

List the elements of the following sets in Roster form:
(i) The set of all positive integers which are multiples of 7.
(ii) The set of all prime numbers less than 20.

Answer 1

(i) The set of all positive integers which are multiples of 7 in roster form is $\{7,14,21,28,...\}$
(ii) The set of all prime numbers less than 20 in roster form is
$\{2,3,5,7,11,13,17,19\}$