NIFT UG 2020 Question Paper with solutions

Work done by $\mathit{Q}$ and $\mathit{R}$ in 6 days $=6\times \frac{7}{60}=\frac{7}{10}$
$\therefore$ Remaining $1-\frac{7}{10}=\frac{3}{10}$ th of work done by $\mathit{P}$ in 3 days.
Since, $\mathit{P}$ alone can do the work in 10 days.
$\therefore \mathit{Q}$ alone can do the work in $\frac{10\times 6}{10-6}=15$ days
$\therefore \mathit{R}$ alone can do the work in $\frac{15\times \frac{60}{7}}{15-\frac{60}{7}}=20$ days
$\therefore$ Difference $=20-10=10$ days