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If x persons take y day to complete z similar jobs, how long

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If x persons take y day to complete z similar jobs, how long

by BTGmoderatorLU » Tue May 29, 2018 2:42 pm

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If x persons take y days to complete z similar jobs, how long does it take y persons to complete 1 such job?

A. z
B. x
C. x/y
D. z/x
E. x/z

The OA is E.

x person - z jobs in y days
x person - 1 job in y/z days
1 person - 1 job in y/zx days
y person - 1 job in y^2/zx
Am I missing something ?? Isn't the right way to do it ?? Can anyone assist me, please? Thanks in advance!
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If x persons take y days to complete z similar jobs, how lon

by Keith@ThePrincetonReview » Tue May 29, 2018 5:12 pm
BTGmoderatorLU wrote:If x persons take y days to complete z similar jobs, how long does it take y persons to complete 1 such job?

A. z
B. x
C. x/y
D. z/x
E. x/z

The OA is E.

x person - z jobs in y days
x person - 1 job in y/z days
1 person - 1 job in y/zx days
y person - 1 job in y^2/zx
Am I missing something ?? Isn't the right way to do it ?? Can anyone assist me, please? Thanks in advance!
To remove any guesswork from the question, Plug In values for x, y, and z.

Let x = 2, y = 3, and z = 6, so that 2 people take 3 days to complete 6 jobs.
The question now asks how long it takes y = 3 people to complete 1 job.

If 2 people complete 6 jobs in 3 days, then 1 person completes 3 jobs in 3 days, or 1 job per day.
Therefore, 3 people working together can complete 1 job in 1/3 day.

Plug x = 2, y = 3, and z = 6 into each of the answer choices, looking for the choice that equals 1/3.
Choice A is z = 6, so eliminate choice A.
Choice B is x = 2, so eliminate choice B.
Choice C is x/y, or 2/3, so eliminate choice C.
Choice D is z/x, or 6/2, so eliminate choice D.
Choice E is x/z, or 2/6, so keep choice E.
The correct answer is choice E.
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by Jeff@TargetTestPrep » Thu May 31, 2018 3:21 pm
BTGmoderatorLU wrote:If x persons take y days to complete z similar jobs, how long does it take y persons to complete 1 such job?

A. z
B. x
C. x/y
D. z/x
E. x/z
We are given that x people take y days to complete z similar jobs. Since rate = work/time, we can determine the rate of x people:

rate of x people = z/y

To determine the rate for y people to complete 1 job, we can use a proportion to determine the rate of y people, in which n = the rate of y people. Our proportion read as:

"x people is to a rate of z/y as y people is to a rate of n"

x/(z/y) =y/n

xn = y(z/y)

xn = z

n = z/x

Since we have the rate of y people, we now can determine the time it takes for y people to complete 1 job.

time = work/rate

time = 1/(z/x) = x/z

Answer: E

Jeffrey Miller
Head of GMAT Instruction
[email protected]

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