A machine P can print one lakh books in eight hours, a machine Q can print the same number of books in ten hours, and a machine R can print the same number of books in twelve hours. All of the machines start at 9 a.m., with the exception of machine P, which closes at 11 a.m. with the remaining two machines finishing their job. When do you think the job (to print one lakh books) will be completed?
A. 11:30 A.M.
B. 12 noon
C. 12:30 P.M.
D. 1:00 P.M.
Answer:D
A machine P can print one lakh books in eight hours, a machine Q can print the same number of books in ten hours, and a machine R can print the same number of books in twelve hours. All of the machines start at 9 a.m., with the exception of machine P, which closes at 11 a.m. with the remaining two machines finishing their job. When do you think the job (to print one lakh books) will be completed?
A. 11:30 A.M. B. 12 noon C. 12:30 P.M. D. 1:00 P.M.
Explanation: 1 hour's labour for (P + Q + R) =(1/8+1/10+1/12) =37/120P, Q, and R completed their work in 2 hours =(37/120 x 2) =37/60.Work remaining = (1 - 37/60)=23/60.1 hour's labour for (Q + R) =(1/10 +112)=11/60.Q and R now do 11/60 of the task in 1 hour.Q and R will complete 23/60 of the job in (60/11x23/60) = 23/11 hours = 2 hours. As a result, the job will be finished after 2 hours.