Each set $X_r$ contains $5$ elements and each set $Y_r$ contains $4$ elements and $\bigcup_{r = 1}^{24} X_r = S = \bigcup_{r = 1}^n Y_r$. If each element of set $S$ belongs to exactly $10$ of the $X_r$'s and to exactly $6$ of the $Y_r$'s,then $n$ is equal to:

If $A$ and $B$ are two sets such that $A$ has $40$ elements,$A \cup B$ has $60$ elements and $A \cap B$ has $10$ elements,how many elements does $B$ have?

The range of $f(x) = \cos x - \sin x$ is

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

Range of the function $f(x) = \frac{1}{2 - \sin 3x}$ is

In a class of $55$ students,the number of students studying different subjects are $23$ in Mathematics,$24$ in Physics,$19$ in Chemistry,$12$ in Mathematics and Physics,$9$ in Mathematics and Chemistry,$7$ in Physics and Chemistry and $4$ in all the three subjects. The number of students who have taken exactly one subject is