EPFO 2015 English Medium Solved Paper

Let a man covers d ’ distance in 't‘ time with the speed of V '. So,
$\mathit{v}=\frac{\mathit{d}}{\mathit{t}}$ .........(i)
According to the question, $\frac{3\mathit{v}}{4}=\frac{\mathit{d}}{\mathit{t}+20}$ ........(ii)
Eq. (i) divides by Eq. (ii)
$\frac{\mathit{v}}{\frac{3\mathit{v}}{4}}=\frac{\frac{\mathit{d}}{\mathit{t}}}{\frac{\mathit{d}}{\mathit{t}+20}}$
$\Rightarrow \frac{4}{3}=\frac{\mathit{t}+20}{\mathit{t}}$
$\Rightarrow 4\mathit{t}=3\mathit{t}+60$
$\therefore$ $\mathit{t}=60\min$
Hence, required time to reach office at his usual speed is 60 min.