6 Machines

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fourteenstix Senior | Next Rank: 100 Posts Default Avatar
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6 Machines

Post Sat Sep 28, 2013 2:41 pm
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    Post Sat Sep 28, 2013 3:40 pm
    Quote:
    6 machines working at a constant rate can complete a job in 12 days. How many additional machines working at the same constant rate are needed to complete the job in 8 days?

    A) 2
    B) 3
    C) 4
    D) 6
    E) 8
    If 6 machines take 12 days to complete the job, then we can say that the job takes 72 "machine days" to complete the job (6x12=72)

    To complete the job in 8 days would require 9 machines (72 machine days divided by 8)

    So, we need an additional 3 machines.

    Answer = B

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    Brent

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    theCodeToGMAT Legendary Member
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    Post Sat Sep 28, 2013 7:56 pm
    Work of 6 Machines = Rate x Time = 6 x 12 = 72

    Work of N Machines = N x 8

    Since total work is same so equating:
    72 = N x 8 ==> 9
    Additional Machines 9 - 6 = 3
    Answer {B}

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    vinay1983 Legendary Member
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    Post Sat Sep 28, 2013 10:14 pm
    No.of machines is inversely proportional to the no. of days required

    More machines less days

    so

    12/8*6= 9 machines in total are required so additional machines required are 9-6=3

    B

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