Question : The value of $\frac{1}{4-\sqrt{15}}-\frac{1}{\sqrt{15}-\sqrt{14}}+\frac{1}{\sqrt{14}-\sqrt{13}}-\frac{1}{\sqrt{13}-\sqrt{12}}+\frac{1}{\sqrt{12}-\sqrt{11}}-\frac{1}{\sqrt{11}-\sqrt{10}}+\frac{1}{\sqrt{10}-3}-\frac{1}{3-\sqrt{8}}$ is:

Question : If $4 \tan \theta=3$, then $\frac{4 \sin \theta-\cos \theta+1}{4 \sin \theta+\cos \theta-1}=?$

Question : Which of the following is the smallest ratio?
$\frac{5}{6}, \frac{7}{9}, \frac{11}{12}, \frac{13}{18}$

Question : If $x-\frac{1}{x}=5, x \neq 0$, then what is the value of $\frac{x^6+3 x^3-1}{x^6-8 x^3-1} ?$

Question : A person from the top of a hill observes a vehicle moving towards him at a uniform speed. It takes 10 minutes for the angle of depression to change from $45^{\circ}$ to $60^{\circ}$. After this, the time required by the vehicle to reach the bottom of the hill is: