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GMAT Prep Question (work)

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Junior | Next Rank: 30 Posts
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by gxj007 » Sat Aug 22, 2009 11:27 am
If anyone can explain how to work through this problem, that would very helpful. thanks!


Six machines, each working at the same constant rate, together can complete a certain job in 12 days. How many additional machines, each working at the same constant rate, will be needed to complete the job in 8 days?

a)2
b)3
c)4
d)6
e)8


Answer:
b)3
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Re: GMAT Prep Question (work)

by arbiter » Sat Aug 22, 2009 11:30 am
gxj007 wrote:If anyone can explain how to work through this problem, that would very helpful. thanks!


Six machines, each working at the same constant rate, together can complete a certain job in 12 days. How many additional machines, each working at the same constant rate, will be needed to complete the job in 8 days?

a)2
b)3
c)4
d)6
e)8


Answer:
b)3
if 6 machines takes 12 days
1 machine will take 12/6=2 days

2 days are taken by 1 machine to finish the job
therfore, 8 days are taken by (1/2)*8=4 machine
arbiter
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Re: GMAT Prep Question (work)

by shahdevine » Sat Aug 22, 2009 11:36 am
gxj007 wrote:If anyone can explain how to work through this problem, that would very helpful. thanks!


Six machines, each working at the same constant rate, together can complete a certain job in 12 days. How many additional machines, each working at the same constant rate, will be needed to complete the job in 8 days?

a)2
b)3
c)4
d)6
e)8


Answer:
b)3
(machine1 x time1/job2)=(machine1xtime1/job1)
6x12/1=8M
m=9

so additional machines = 9-6=3 -->D

you got this man!
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by arbiter » Sat Aug 22, 2009 11:46 am
yea u are right!
basically , total work done in 1 day = 12*6=72 =x*8
=>x=9 machines.
Extra 9-6=3
arbiter
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