Write the set $\{ x:x$ is a positive integer and ${x^2} < 40\} $ in the roster form.

State which of the following sets are finite or infinite :

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

State whether each of the following set is finite or infinite :

The set of letters in the English alphabet

Match each of the set on the left 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 $6\} $
$(ii)$ $\{2,3\}$	$(b)$ $\{ x:x$ is an odd natural number less than $10\} $
$(iii)$ $\{ M , A , T , H , E , I , C , S \}$	$(c)$ $\{ x:x$ is natural number and divisor of $6\} $
$(iv)$ $\{1,3,5,7,9\}$	$(d)$ $\{ x:x$ a letter of the work $\mathrm{MATHEMATICS}\} $

Write down all the subsets of the following sets

$\{ a\} $

Write the following sets in roster form :

$\mathrm{F} =$ The set of all letters in the word $\mathrm{BETTER}$