Question
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 ?
Answer: Option D
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(P + Q + R)'s 1 hours work = `(1/8 + 1/10 + 1/12) = 37/120`
Work done by P, Q and R in 2 hours = `(37/120 xx 2) = 37/60`
Remaining work = `(1 - 37/60) = 23/60`
(Q + R)'s 1 hours work = `(1/10 + 1/12) = 11/60`
Now , `11/60` work is done by Q and R in 1 hour
So, `23/60` work will be done by Q and R in `(60/11 xx 23/60) = 23/11` hours = 2 hours.
So, the work will be finished approximately 2 hours after 11 a.m. , i.e. around 1 p.m.
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