Let $A =\{1,2,3, \ldots \ldots, 10\}$ and $B=\left\{\frac{m}{n}: m, n \in A, m < n \text { and } \operatorname{gcd}(m, n)=1\right\} . $Then $n(B)$ is equal to :

If $A$ and $B$ are any two non empty sets and $A$ is proper subset of $B$. If $n(A) = 4$, then minimum possible value of $n(A \Delta B)$ is (where $\Delta$ denotes symmetric difference of set $A$ and set $B$)

Let $A=\{1,2,3,4,5,6\} .$ Insert the appropriate symbol $\in$ or $\notin$ in the blank spaces:

$ 4\, ......... \, A $

Write the following sets in the set-builder form :

${\rm{\{ 5,25,125,625\} }}$

Let $A=\{1,2,\{3,4\}, 5\} .$ Which of the following statements are incorrect and why ?

$1 \in A$

Are the following pair of sets equal ? Give reasons.

$A = \{ x:x$ is a letter in the word ${\rm{FOLLOW }}\} $

$B = \{ y:y$ is a letter in the word $WOLF\} $