JIPMAT (QA) PYQs

The value of $(\frac{1}{\sqrt{9}-\sqrt{8}} - \frac{1}{\sqrt{8}-\sqrt{7}} + \frac{1}{\sqrt{7}-\sqrt{6}} - \frac{1}{\sqrt{6}-\sqrt{5}} + \frac{1}{\sqrt{5}-\sqrt{4}})$ is

The sum of $n-$ terms of sequence $\frac{1}{1 \times 2}+\frac{1}{2 \times 3}+\frac{1}{3 \times 4} \ldots \ldots$. Is

If the $m^{\text{th}}$ term of an arithmetic progression is $\frac{1}{n}$ and the $n^{\text{th}}$ term is $\frac{1}{m}$, then the $mn^{\text{th}}$ term of this progression will be