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 350,000 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:

x2y = 10,000y – 100xy [multiplying by the common denominator 10,000] x2y + 100xy – 10,000y = 0 [everything to one side, because it’s quadratic] y(x2 + 100x – 10,000) = 0 [factoring] Therefore, the answer to the prompt question is affirmative if either x2 + 100x – 10,000 = 0 or y = 0.

(1) SUFFICIENT: This statement rearranges to give = 0.

(2) INSUFFICIENT: y cannot be 0, but no information is provided about x, making it impossible to determine whether x2 + 100x – 10,000 = 0.

Re: MGMAT test 4: X Percent of X Percent [#permalink]
21 Jun 2010, 16:06

Expert's post

1

This post was BOOKMARKED

zisis wrote:

Is x% of x% of y equal to x% less than y ?

(1) x(x + 100) = 10,000 (2) y(y + 1) = 1

OA: A

x2y = 10,000y – 100xy [multiplying by the common denominator 10,000] x2y + 100xy – 10,000y = 0 [everything to one side, because it’s quadratic] y(x2 + 100x – 10,000) = 0 [factoring] Therefore, the answer to the prompt question is affirmative if either x2 + 100x – 10,000 = 0 or y = 0.

(1) SUFFICIENT: This statement rearranges to give = 0.

(2) INSUFFICIENT: y cannot be 0, but no information is provided about x, making it impossible to determine whether x2 + 100x – 10,000 = 0.

But, I believe D: A sufficient B: y=1 or y+1=1 therefore y=0 therefore B sufficient...

what am i missing? please help

Question: is \(\frac{x}{100}*\frac{x}{100}*y=y(1-\frac{x}{100})\)? --> is \(x^2y=100y(100-x)\)? --> is \(x^2y=y(10,000-100x)\) --> is \(y(x^2+100x-10,000)=0\)?

Basically question is does \(y=0\) or/and \(x^2+100x-10,000=0\)?

(2) \(y(y+1)=1\). Here it's clear that \(y\neq{0}\), (substitute \(y=0\) in this equation: \(0(0+1)=0\neq{1}\)). So we know that \(y\neq{0}\), but don't know whether \(x^2+100x-10,000=0\)? Not sufficient.

To elaborate more: the problem with your solution is that you solved incorrectly \(y(y+1)=1\). \(y(y+1)=1\) --> \(y^2+y-1=0\) --> solving for \(y\): \(y=\frac{-1-\sqrt{5}}{2}\) or \(y=\frac{-1+\sqrt{5}}{2}\), so \(y\neq{0}\).

Re: MGMAT test 4: X Percent of X Percent [#permalink]
07 Jul 2012, 03:22

Bunuel wrote:

zisis wrote:

Is x% of x% of y equal to x% less than y ?

(1) x(x + 100) = 10,000 (2) y(y + 1) = 1

OA: A

x2y = 10,000y – 100xy [multiplying by the common denominator 10,000] x2y + 100xy – 10,000y = 0 [everything to one side, because it’s quadratic] y(x2 + 100x – 10,000) = 0 [factoring] Therefore, the answer to the prompt question is affirmative if either x2 + 100x – 10,000 = 0 or y = 0.

(1) SUFFICIENT: This statement rearranges to give = 0.

(2) INSUFFICIENT: y cannot be 0, but no information is provided about x, making it impossible to determine whether x2 + 100x – 10,000 = 0.

But, I believe D: A sufficient B: y=1 or y+1=1 therefore y=0 therefore B sufficient...

what am i missing? please help

Question: is \(\frac{x}{100}*\frac{x}{100}*y=y(1-\frac{x}{100})\)? --> is \(x^2y=100y(100-x)\)? --> is \(x^2y=y(10,000-100x)\) --> is \(y(x^2+100x-10,000)=0\)?

Basically question is does \(y=0\) or/and \(x^2+100x-10,000=0\)?

(2) \(y(y+1)=1\). Here it's clear that \(y\neq{0}\), (substitute \(y=0\) in this equation: \(0(0+1)=0\neq{1}\)). So we know that \(y\neq{0}\), but don't know whether \(x^2+100x-10,000=0\)? Not sufficient.

To elaborate more: the problem with your solution is that you solved incorrectly \(y(y+1)=1\). \(y(y+1)=1\) --> \(y^2+y-1=0\) --> solving for \(y\): \(y=\frac{-1-\sqrt{5}}{2}\) or \(y=\frac{-1+\sqrt{5}}{2}\), so \(y\neq{0}\).

Answer: A.

Hope it's clear.

Can you explain this part \(\frac{x}{100}*\frac{x}{100}*y=y(1-\frac{x}{100})\)? --> my R.H.S of equation is coming as y-x/100 kindly correct me if i am wrong _________________

_______________________________________________________________________________________________________________________________ If you like my solution kindly reward me with Kudos.

Re: MGMAT test 4: X Percent of X Percent [#permalink]
07 Jul 2012, 03:27

1

This post received KUDOS

Expert's post

riteshgupta wrote:

Bunuel wrote:

zisis wrote:

Is x% of x% of y equal to x% less than y ?

(1) x(x + 100) = 10,000 (2) y(y + 1) = 1

OA: A

x2y = 10,000y – 100xy [multiplying by the common denominator 10,000] x2y + 100xy – 10,000y = 0 [everything to one side, because it’s quadratic] y(x2 + 100x – 10,000) = 0 [factoring] Therefore, the answer to the prompt question is affirmative if either x2 + 100x – 10,000 = 0 or y = 0.

(1) SUFFICIENT: This statement rearranges to give = 0.

(2) INSUFFICIENT: y cannot be 0, but no information is provided about x, making it impossible to determine whether x2 + 100x – 10,000 = 0.

But, I believe D: A sufficient B: y=1 or y+1=1 therefore y=0 therefore B sufficient...

what am i missing? please help

Question: is \(\frac{x}{100}*\frac{x}{100}*y=y(1-\frac{x}{100})\)? --> is \(x^2y=100y(100-x)\)? --> is \(x^2y=y(10,000-100x)\) --> is \(y(x^2+100x-10,000)=0\)?

Basically question is does \(y=0\) or/and \(x^2+100x-10,000=0\)?

(2) \(y(y+1)=1\). Here it's clear that \(y\neq{0}\), (substitute \(y=0\) in this equation: \(0(0+1)=0\neq{1}\)). So we know that \(y\neq{0}\), but don't know whether \(x^2+100x-10,000=0\)? Not sufficient.

To elaborate more: the problem with your solution is that you solved incorrectly \(y(y+1)=1\). \(y(y+1)=1\) --> \(y^2+y-1=0\) --> solving for \(y\): \(y=\frac{-1-\sqrt{5}}{2}\) or \(y=\frac{-1+\sqrt{5}}{2}\), so \(y\neq{0}\).

Answer: A.

Hope it's clear.

Can you explain this part \(\frac{x}{100}*\frac{x}{100}*y=y(1-\frac{x}{100})\)? --> my R.H.S of equation is coming as y-x/100 kindly correct me if i am wrong

Consider this: 10% less than \(y\) is \(y*(1-\frac{10}{100})=y*0.9\), the same way "\(x%\) less than \(y\)": is \(y(1-\frac{x}{100})\).

Re: Is x% of x% of y equal to x% less than y ? (1) x(x + 100) = [#permalink]
09 Dec 2012, 06:09

Expert's post

morfin wrote:

I do not understand the question. Why did you rephrase the question FROM "Is x% of x% of y equal to x% less than y ?" TO Is y = 0 ?

When I read the question, I wrote down (x%((x%)y)) = x%<y

Please help. thanks in advance.

"Is x% of x% of y equal to x% less than y?" means is \(\frac{x}{100}*\frac{x}{100}*y=y(1-\frac{x}{100})\)?

If you manipulate with this expression as shown above the questions becomes: is \(y(x^2+100x-10,000)=0\)? So, the question basically asks whether \(y=0\) or/and \(x^2+100x-10,000=0\)?

Re: Is x% of x% of y equal to x% less than y ? [#permalink]
17 Oct 2013, 05:31

Expert's post

adg142000 wrote:

my approach for the above was i reduced the word statement to equation with statement 1 as :

\(xy/(x+100)=y(1-x/100)\)? ,,and took the values x=10 and y =10 for which 100/110< 9

but for x=10 and y=-10

-100/110 is not less than -9.

I got this problem wrong for this reason. Do for percentage problems -ve sign has to be ignored???

Plugging-in is not the correct approach for this question, as because the values of x and y are fixed by the fact statements.

We have to prove whether \(\frac{x}{100}*\frac{x}{100}*y = y*(1-\frac{x}{100})\) or not --> \(\frac{x}{100}*y[\frac{x}{100}*+1] = y\) \(\to\)After re-arranging we get

\(x*(x+100)*y = 10000y \to Is y*[x*(x+100)-10000]=0?\)

From F.S 1, we know that x*(x+100) = 10000, thus Sufficient.

From F.S 2, we know only the value of y, and nothing about x. Insufficient

A.

I believe negative percentage makes sense when there is a decrease . So it will not be wrong to say for example that the decrease in the value was 5% or the percentage change was -5%. _________________

How the growth of emerging markets will strain global finance : Emerging economies need access to capital (i.e., finance) in order to fund the projects necessary for...

One question I get a lot from prospective students is what to do in the summer before the MBA program. Like a lot of folks from non traditional backgrounds...