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njvenkatesh
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GMATPrep Question 16 Jun 2006, 10:27
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Can someone helpme with this question ?

Thanks in advance.



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shobhitb
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GMATPrep Question 16 Jun 2006, 10:40
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10*1/x = 16
x=160

8*1/160 = 1/20 work each hour - hence 20 hours
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GMATPrep Question 16 Jun 2006, 11:01
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Let's say each of the machine takes x hrs to complete the job.
So, in 1 hr one machine completes (1/x) amount of job.
Therefore in 1 hr, ten machines will complete 10*(1/x) amount of job --------> (1)
In question, its given that ten machines complete the job in 16 hrs.
So in 1 hrs, ten machines will complete (1/16) amount of job ------------> (2)

Equating (1) and (2):

10*(1/x) = (1/16)
=> x = 160

That means each machine takes 160 hrs to complete the job.
Now, in 1 hr , each machine completes 1/160 amount of job. ------------> (3)
So in 1 hrs, Eight machines will complete 8*(1/160) amount of job ------------> (4)

Let's say, Eight machines will complete the job in y hrs.
So in 1 hr, Eight machines will complete 1/y amount of job. -----------> (5)

Equating (4) and (5):

8*(1/160) = 1/y
=> y = 20

So, Eight machines will complete the job in 20 hrs.

Regards,
Brajesh
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GMATPrep Question 16 Jun 2006, 11:49
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10 machines take 16 hours to do 1 job.
10 machines do 1/16 of the job per hour.
1 machine does 1/160 of the job per hour.

If we have 8 machines, 8*1/160 = 1/20. They will complete 1/20 of the job per hour.

Thus, it'll take 8 machines 20 hours to complete 1 job.
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GMATPrep Question 16 Jun 2006, 13:10
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20

10 machines do a job in = 16 hours
1 machine do a job in = 10 * 16 = 160 hours
8 machines do a job in 160/8 = 20 hours
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GMATPrep Question 16 Jun 2006, 13:58
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Let r be rate of each machine

Therefore given job takes 16hrs together...

i.e. 1/10r = 16 => r = 1/160


For 8 machines time taken = 1/8xr = 160/8 = 20hrs



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Hi there,
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