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:

The answer is A. 1) (r+s) / rs = 4 => (r/rs) + (s/rs) = 4 => (1/r) + (1/s) = 4 SUFFICIENT 2) plug in r=s=1/2, you get 4=4. But plug in r=s=1, you get 2=4. INSUFFICIENT.

For me the answer is A
r+s=4rs
dividing both sides by rs
r/rs+s/rs=4
1/r+1/s=4 (Sufficient)
r=s
Different values of r or s suggest that 1/r+1/s may or may not be =4 thus insufficient
so Answer is A

The answer is A. 1) (r+s) / rs = 4 => (r/rs) + (s/rs) = 4 => (1/r) + (1/s) = 4 SUFFICIENT 2) plug in r=s=1/2, you get 4=4. But plug in r=s=1, you get 2=4. INSUFFICIENT.

gar!! failed to see that...

why can't we just answer this question w/the info provided in the stem? did we really need additional info to figure that out? 1/r + 1/s = 4 => s/rs + r/rs = 4 => 1/r + 1/s = 4

Well we could certainly have done it that way Fig if the stem had told us that 1/r+1/s is indeed equal to 4. The stem is asking whether the expression is a true equation or not. And to validate the stem we are provided with two different sets of information which are statements A & B.
Actually this is how i had made D the correct option by putting r=s in the stem. But as u see, stem is not stated to be true, it is asked wherther it is true or not.
I hope this explains ur question.

sorry dude
u see when the boss is just around the corner, then such mistakes are bound to happen. Especially when ur boss is more like a blood hound, who only wnats ur blood instead of ur sweat.
And yes u did make it more difficult. It happens to me too. simple solution is in fornt of me, but i start making complex equations.

1) (r+s)/rs= 4rs/rs = 4, SUF
2) r=s, from the stem => 1/r, but since we do not know how much does r worth we also do not know how much 1/r worths, INSUF.

Re: if rs is not equal to 0, is 1/r + 1/s = 4? 1) r+s = 4rs 2) r [#permalink]

Show Tags

23 Feb 2014, 02:32

Expert's post

shiblee wrote:

r+s=4 rs or (r+s)/rs=4 or (r/rs)+(s/rs)=4 or 1/r+1/s=4 . so sufficient .

statements 2 is clearly out . correct answer = A .

if this portion of the question " rs is not equal to 0 " is not given , then ? what would happen ?

Posted from my mobile device

If rs#0, is 1/r + 1/s = 4 ?

Question: is \(\frac{1}{r}+\frac{1}{s}=4\) --> is \(\frac{r+s}{rs}=4\) --> is \(r+s=4rs\)?

(1) \(r+s=4rs\), directly answers the question. Sufficient.

(2) \(r = s\), the question becomes: is \(\frac{1}{r}+\frac{1}{r}=4\) ? --> is \(r=\frac{1}{2}\)? but we dont' know whether \(r=\frac{1}{2}\). Not sufficient.

Answer: A.

As for your question: if rs#0 were not given, then r=s=0 would be possible and in this case 1/r + 1/s would be undefined.

http://blog.ryandumlao.com/wp-content/uploads/2016/05/IMG_20130807_232118.jpg The GMAT is the biggest point of worry for most aspiring applicants, and with good reason. It’s another standardized test when most of us...

With the limited financing options available to NZ citizens (especially those comme moi who aren't planning to return to work in NZ), I've really had to...

Strategy, innovation, marketing, finance... The second module has been pretty engaging. Though, no lack of memorable times. There is no lack of high profile guest speakers. One of the...