Symbiosis National Aptitude Test SNAP 2019 Paper

Let Mitesh finish a work in n days then Ritesh finish the same work in (n – 30) days
ATQ,
$2\times \frac{1}{\mathit{n}}$ = $\frac{1}{\left(\mathit{n}-30\right)}$
2(n – 30) = n
⇒ n = 60
So, Mitesh finish the work in 60 days
and Ritesh finish the work in 30 days
Time taken by them to finish the work, while working together
= $\frac{60}{2+1}$ = $\frac{60}{3}$
= 20 days