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?
(P + Q + R)’s 1 hour’s work
=
Work done by P, Q and R in 2 hours
=
Remaining work
=
(Q + R)’s 1 hour’s work
=
Now, ¹¹⁄₆₀work is done by Q and R in 1 hour.
So, ²³⁄₆₀ work will be done by Q and R in
hours ≈ 2 hours.
So, the work will be finished approximately 2 hours after 11 a.m., i.e., around 1 p.m.