RRB NTPC Mains or Stage 2 Model Paper 9 with solutions

(d) (P + Q + R)’s 1 hour’s work =
$\left[\frac{1}{8}+\frac{1}{10}+\frac{1}{12}\right]=\frac{37}{120}$
Work done by P, Q and R in 2 hours =
$\left[\frac{37}{120}\times 2\right]=37./60$Remaining work =$\left[1-\frac{37}{60}\right]=\frac{23.}{60}$
(Q + R)’s 1 hour’s work
$=\left[\frac{1}{10}+\frac{1}{12}\right]=11./60$
Now, $\frac{11}{60}$work is done by Q and R in 1hour.
So, $\frac{23}{60}$work will be done by Q and R in
$\left[\frac{60}{11}\times \frac{23}{60}\right]=\frac{23}{11}$hours ≈ 2 hours.
So, the work will be finished approximately 2 hours after 11 a.m., i.e., around 1 p.m.