Symbiosis National Aptitude Test SNAP 2019 Paper

6 mobiles are packed in 6 minutes by 6 staff.
So, 1 mobile is packed in 6 minutes by 1 staff.
∴ 60 mobiles are packed in 60 minutes by 6 staff.
Trick : $\frac{{\mathit{n}}_{1.}{\mathit{w}}_1}{{\mathit{d}}_1}:\frac{{\mathit{n}}_{2.}{\mathit{w}}_2}{{\mathit{d}}_2}$
$\frac{6\times 6}{6}$ = $\frac{60\times {\mathit{n}}_2}{60}$
∴ ${\mathit{n}}_2$ = 6