Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized for You

we will pick new questions that match your level based on your Timer History

Track Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 500,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

Question: If x, y, and z are integers greater than 0 and x = y + z, what is the value of (y-z)/y?

(1) (x-y)/y=4/5 (2) z/y=4/5

A)Statement (1) ALONE is sufficient, but statement (2) is not sufficient. B)Statement (2) ALONE is sufficient, but statement (1) is not sufficient. C)BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient. D)EACH statement ALONE is sufficient. E)Statements (1) and (2) TOGETHER are NOT sufficient.

Data from question stem: x = y + z. Since we need the value of \(1 - \frac{z}{y}\), let us divide this equation by y. We get \(\frac{x}{y} = 1 + \frac{z}{y}\)

Question: What is \(\frac{(y-z)}{y} = 1 - \frac{z}{y}\) To get z/y, we should either have x/y (as seen above) or z/y

1.\(\frac{(x - y)}{y} = \frac{4}{5}\) or \(\frac{x}{y} - 1 = \frac{4}{5}\) From here, we get the value of x/y. Sufficient.

2. This directly gives us the value of z/y. Sufficient. Answer (D) _________________

now given x= y+z so if \(\frac{x}{y} = \frac{9}{5}\) then we can take x= 9 and y=5 then z=4 here \(\frac{z}{y} =\frac{4}{5}\)

but if \(\frac{x}{y} = \frac{9}{5}\)then we can also take x= 18 and z=10 can't we? then z= 8 here \(\frac{z}{y} =\frac{8}{10}\)

So I thought statement 1 did not give us the actual values of x and y, so I thought there were many possibilities hence marked statement as insufficient.

so this was my confusion , I though since we got a ratio at the end of simplification of 1 we do not know the actual values of x and y , since we got \(\frac{x}{y} = \frac{9}{5}\), \(\frac{x}{y}\) could also be \(\frac{18}{10}\),or \(\frac{27}{15}\), if x and y differs so will z and hence will \(\frac{z}{y}\) unless we are always reducing ratios to their lowest form

please tell me how can we be sure of x and y from this ratio

thanks

Notice that we need to find the ratio of z to y (z/y). Now, you are right, we CANNOT get the VALUES of x, y, and z, from x=y+z and (x-y)/y=4/5, but we CAN get the RATIO of z to y (as shown in my post).

Does this make sense?

So we are taking \(\frac{x}{y} = \frac{9}{5} =\frac{18}{10} =\frac{27}{15}\)

if we are taking all these to be equal, then ratio's are being reduced to their lowest forms.

That was my original question. " Do we need to reduce ratio's to the lowest forms " The answer must be yes, because if the answer is no then \(\frac{9}{5}\) would not be equal \(\frac{18}{10}\) , and different values of x and y would give different values of z, and we would have different \(\frac{z}{y}\)

So yes , ratio's must be reduced to their lowest forms,Please can you reaffirm.

No, that's not correct. You don't have to reduce. 9/5 is the same ratio as 18/10.

If you consider x/y=18/10, you'll get that z/y=8/10, which is the same as 4/5. _________________

now given x= y+z so if \(\frac{x}{y} = \frac{9}{5}\) then we can take x= 9 and y=5 then z=4 here \(\frac{z}{y} =\frac{4}{5}\)

but if \(\frac{x}{y} = \frac{9}{5}\)then we can also take x= 18 and z=10 can't we? then z= 8 here \(\frac{z}{y} =\frac{8}{10}\)

So I thought statement 1 did not give us the actual values of x and y, so I thought there were many possibilities hence marked statement as insufficient.

so this was my confusion , I though since we got a ratio at the end of simplification of 1 we do not know the actual values of x and y , since we got \(\frac{x}{y} = \frac{9}{5}\), \(\frac{x}{y}\) could also be \(\frac{18}{10}\),or \(\frac{27}{15}\), if x and y differs so will z and hence will \(\frac{z}{y}\) unless we are always reducing ratios to their lowest form

please tell me how can we be sure of x and y from this ratio

now given x= y+z so if \(\frac{x}{y} = \frac{9}{5}\) then we can take x= 9 and y=5 then z=4 here \(\frac{z}{y} =\frac{4}{5}\)

but if \(\frac{x}{y} = \frac{9}{5}\)then we can also take x= 18 and z=10 can't we? then z= 8 here \(\frac{z}{y} =\frac{8}{10}\)

So I thought statement 1 did not give us the actual values of x and y, so I thought there were many possibilities hence marked statement as insufficient.

so this was my confusion , I though since we got a ratio at the end of simplification of 1 we do not know the actual values of x and y , since we got \(\frac{x}{y} = \frac{9}{5}\), \(\frac{x}{y}\) could also be \(\frac{18}{10}\),or \(\frac{27}{15}\), if x and y differs so will z and hence will \(\frac{z}{y}\) unless we are always reducing ratios to their lowest form

please tell me how can we be sure of x and y from this ratio

thanks

Notice that we need to find the ratio of z to y (z/y). Now, you are right, we CANNOT get the VALUES of x, y, and z, from x=y+z and (x-y)/y=4/5, but we CAN get the RATIO of z to y (as shown in my post).

now given x= y+z so if \(\frac{x}{y} = \frac{9}{5}\) then we can take x= 9 and y=5 then z=4 here \(\frac{z}{y} =\frac{4}{5}\)

but if \(\frac{x}{y} = \frac{9}{5}\)then we can also take x= 18 and z=10 can't we? then z= 8 here \(\frac{z}{y} =\frac{8}{10}\)

So I thought statement 1 did not give us the actual values of x and y, so I thought there were many possibilities hence marked statement as insufficient.

so this was my confusion , I though since we got a ratio at the end of simplification of 1 we do not know the actual values of x and y , since we got \(\frac{x}{y} = \frac{9}{5}\), \(\frac{x}{y}\) could also be \(\frac{18}{10}\),or \(\frac{27}{15}\), if x and y differs so will z and hence will \(\frac{z}{y}\) unless we are always reducing ratios to their lowest form

please tell me how can we be sure of x and y from this ratio

thanks

Notice that we need to find the ratio of z to y (z/y). Now, you are right, we CANNOT get the VALUES of x, y, and z, from x=y+z and (x-y)/y=4/5, but we CAN get the RATIO of z to y (as shown in my post).

Does this make sense?

So we are taking \(\frac{x}{y} = \frac{9}{5} =\frac{18}{10} =\frac{27}{15}\)

if we are taking all these to be equal, then ratio's are being reduced to their lowest forms.

That was my original question. " Do we need to reduce ratio's to the lowest forms " The answer must be yes, because if the answer is no then \(\frac{9}{5}\) would not be equal \(\frac{18}{10}\) , and different values of x and y would give different values of z, and we would have different \(\frac{z}{y}\)

So yes , ratio's must be reduced to their lowest forms,Please can you reaffirm. _________________

No, that's not correct. You don't have to reduce. 9/5 is the same ratio as 18/10.

If you consider x/y=18/10, you'll get that z/y=8/10, which is the same as 4/5.

Well I guess we all have different ways to look at it if x/y=9/5 = 18/10 The fact that their are equal is not easily visible to me, till i get both the numerator and denominator to have the same value as the other ratio's , and that I get when I reduce them

So I guess without reducing them if one can ascertain that the ratio's are same then no need to reduce them.

Main thing is to realize that 9/5 = 18/10 = 27/15

Let me know if I am still missing something, thank you +1 _________________

- Stne

gmatclubot

Re: GOOD DS question
[#permalink]
08 Sep 2013, 06:24

Part 2 of the GMAT: How I tackled the GMAT and improved a disappointing score Apologies for the month gap. I went on vacation and had to finish up a...

Cal Newport is a computer science professor at GeorgeTown University, author, blogger and is obsessed with productivity. He writes on this topic in his popular Study Hacks blog. I was...

So the last couple of weeks have seen a flurry of discussion in our MBA class Whatsapp group around Brexit, the referendum and currency exchange. Most of us believed...