If $A = \{x \mid x \text{ is a prime number, } 0 \leq x \leq 9\}$,then the number of elements of the power set of $A$ is

Match each of the set on the left in the roster form with the same set on the right described in set-builder form:

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

The number of subgroups of the group $(Z_{5}, +_{5})$ is

Make correct statements by filling in the symbols $\subset$ or $\not\subset$ in the blank spaces:
${ x:x \text{ is a triangle in a plane} } \dots { x:x \text{ is a rectangle in the plane} }$

Write the following set in the set-builder form: $\{ 2, 4, 6, \dots \}$

The set $\{n(n+1)(2n+1) : n \in \mathbb{Z}\}$ is a subset of: