129. 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 ?

✅ The correct answer is option D.
(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.