NIFT PG 2020 Question Paper with solutions

$\because$ Time taken by $\mathit{x}$ to copy 80 pages $=20\mathit{h}$
$\therefore$ Time taken by $\mathit{x}$ to copy 20 pages
$=\frac{20}{80}\times 20=5\mathit{h}$
Similarly, time taken by $\mathit{x}$ and $\mathit{y}$ together to copy 20 pages
$=\frac{27}{135}\times 20=4\mathit{h}$
Now, let $\mathit{y}$ can copy 20 pages in $\mathit{n}\mathit{h}$. Then,
$\frac{1}{5}+\frac{1}{\mathit{n}}=\frac{1}{4}$
$\Rightarrow \frac{1}{\mathit{n}}=\frac{1}{4}-\frac{1}{5}=\frac{1}{20}$
$\Rightarrow \mathit{n}=20\mathit{h}$