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Aptitude - Time and Work - Discussion

Discussion Forum : Time and Work - General Questions (Q.No. 10)
Time and Work
10.
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 ?
11:30 A.M.
12 noon
12:30 P.M.
1:00 P.M.
Answer: Option
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.

Discussion:
95 comments Page 10 of 10.
Vachu said:   1 decade ago
Why p is working for two hrs its ont mentioned?
Sameer said:   1 decade ago
P 1hrs work 1/8
Q 1hrs work 1/10
R 1hrs work 1/12

p worked for 2 hrs so 2*1/8
suppose Q and r worked for 'x' hrs
then,
2*1/8+(1/10)*x+(1/12)x = 1
x=4.09
ans 9+4.09 = 1pm
(1)
Jyothi.k said:   1 decade ago
@Sowjanya

11/60 work done by q and r in i hour

Therefore

1 work done by q and r in 60/11 hour

So 23/60 work done by q and r in 60/11*23/60 hours
Pandu said:   1 decade ago
This problem code is length. Please any shortcut of this problem.
Sowjanya said:   1 decade ago
Hey friends. Can any one suggest why 60/11 is multiplied with 23/60?
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