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It takes 6 technicians a total of 10 hours to build and

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Re: It takes 6 technicians a total of 10 hours to build and  [#permalink]

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New post 15 Nov 2016, 20:09
Let's say job = 120 bricks --> Rate of 6 technicians then is --> 120=6R x 10 --> R = 2

5pm: 6(2)(6hrs) = 72
6pm: 6(2)(7hrs)+2 = 86
7pm: 6(2)(8)+2(2) +2 = 102
8pm: 6(2)(9)+2(3)+2(2)+2 =120 BINGO!

Answer is C
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Re: It takes 6 technicians a total of 10 hours to build and  [#permalink]

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New post 08 Feb 2017, 19:44
Hussain15 wrote:
It takes 6 technicians a total of 10 hours to build and program a new server from Direct Computer, with each working at the same rate. If six technicians start to build the server at 11:00 AM, and one technician per hour is added beginning at 5:00 PM, at what time will the server be complete?

A. 7:30 PM
B. 7:45 PM
C. 8:00 PM
D. 9:00 AM
E. 10:00 PM


We are given that 6 technicians can complete a job in 10 hours. Since rate = work/time, the rate of the 6 technicians is 1/10. Thus, the rate of 1 technician is (1/10)/6 = 1/60.

We see that 6 technicians work from 11:00 AM to 5:00 PM, or 6 hours. Since rate x time = work, those technicians complete 1/10 x 6 = 6/10 = 3/5 of the job.

If another technician is added to the job at 5:00 PM, the new rate for the technicians is (1/60) x 7 = 7/60, and thus all 7 technicians complete 7/60 of the job in the hour from 5:00 PM to 6:00 PM.

Thus, 3/5 + 7/60 = 36/60 + 7/60 = 43/60 of the job will be completed.

If another technician is added to the job at 6:00 PM, the new rate for the technicians is (1/60) x 8 = 8/60, and thus all 8 technicians complete 8/60 of the job in the hour from 6:00 PM to 7:00 PM.

Thus, 43/60 + 8/60 = 51/60 of the job will be completed.

If another technician is added to the job at 7:00 PM, the new rate for the technicians is (1/60) x 9 = 9/60, and thus all 9 technicians complete 9/60 of the job in the hour from 7:00 PM to 8:00 PM.

Thus, 51/60 + 9/60 = 60/60 = 1 whole job will be completed at 8:00 PM.

Answer: C
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Re: It takes 6 technicians a total of 10 hours to build and  [#permalink]

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New post 06 Jun 2017, 16:54
Hussain15 wrote:
It takes 6 technicians a total of 10 hours to build and program a new server from Direct Computer, with each working at the same rate. If six technicians start to build the server at 11:00 AM, and one technician per hour is added beginning at 5:00 PM, at what time will the server be complete?

A. 7:30 PM
B. 7:45 PM
C. 8:00 PM
D. 9:00 AM
E. 10:00 PM

1. 1 technician will build in 60 hours or 60 man hours are needed
2. 6 technicians work for first 6 hours which is expending of 36 man hours
3. Similarly in the seventh, eighth , ninth hours, man hours expended are 7,8,9
4. Total man hours expended by the end of ninth hour is 36+7+8+9= 60 which will complete the job.
5. 11 A.M + 9 hrs is 8 PM
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Re: It takes 6 technicians a total of 10 hours to build and  [#permalink]

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New post 29 Aug 2018, 10:36
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

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Re: It takes 6 technicians a total of 10 hours to build and &nbs [#permalink] 29 Aug 2018, 10:36

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