A machine P can print one lakh books in 8 hours, machine Q can print the same number of books in 10 hours while machine R can print them in 12 hours. All the machines are started at 9 a.m. while machine P is closed at 11 a.m. and the remaining two machines complete the work. Approximately at what time will the work be finished?
1 p.m.
(P+Q+R)’s 1 hour’s work =(18+110+112)=37120
Work done by P, Q and R in 2 hours =(37120×2)=3760
Remaining work =(1−3760)=2360
(Q+R)’s 1 hour’s work =(110+112)=1160
Now, 1160 work is done by Q and R in 1 hour
So, 2360 work will be done by Q and R in 6011×2360=2311hours=2 hours.
So, the work will be finished approximately 2 hours after 11 a.m., i.e. at around 1 p.m.