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 work. Approximately at what time will the work (to print one lakh books) be finished ?
[A].11:30 A.M.
12 noon
12:30 P.M.
1:00 P.M.
[A].
[B].
[C].
[D].
Answer: Option D
Explanation:
| (P + Q + R)’s 1 hour’s work = | 1 | + | 1 | + | 1 | = | 37 | . | ||
| 8 | 10 | 12 | 120 |
| Work done by P, Q and R in 2 hours = | 37 | x 2 | = | 37 | . | ||
| 120 | 60 |
| Remaining work = | 1 – | 37 | = | 23 | . | ||
| 60 | 60 |
| (Q + R)’s 1 hour’s work = | 1 | + | 1 | = | 11 | . | ||
| 10 | 12 | 60 |
| Now, | 11 | work is done by Q and R in 1 hour. |
| 60 |
| So, | 23 | work will be done by Q and R in | 60 | x | 23 | = | 23 | hours 2 hours. | ||
| 60 | 11 | 60 | 11 |
So, the work will be finished approximately 2 hours after 11 A.M., i.e., around 1 P.M.