State which of the following sets are finite or infinite :

$\{ x:x \in N$ and $2x - 1 = 0\} $

Write down all the subsets of the following sets

$\{ a,b\} $

In rule method the null set is represented by

Which of the following are sets ? Justify your answer.

The collection of questions in this chapter.

Write the following sets in roster form :

$A = \{ x:x$ is an integer and $ - 3 < x < 7\} $

Let $S=\{1,2,3, \ldots, 40)$ and let $A$ be a subset of $S$ such that no two elements in $A$ have their sum divisible by 5 . What is the maximum number of elements possible in $A$ ?