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.

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:

OA is "A". That's only A is sufficient. but I presume that that answer should be "C" because for me r=s , if I substitute in the equation then

1/r + 1/r = 2/r = 4 r = 1/2 and I am able to prove the condition. Although, OG has taken values of r and s to prove that 2nd condition is not sufficient, then why not try to put some values for r and s in the 1st option too? Please help

OA is "A". That's only A is sufficient. but I presume that that answer should be "C" because for me r=s , if I substitute in the equation then

1/r + 1/r = 2/r = 4 r = 1/2 and I am able to prove the condition. Although, OG has taken values of r and s to prove that 2nd condition is not sufficient, then why not try to put some values for r and s in the 1st option too? Please help

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.

Hi if i go the algebric way on statement 1 i get it right but statement 2 i get it wrong so I am kinda confused eg statement 2 sates r = s

so lets see 1/r + 1/s = 4 can be written as r + s = 4 rs so replacing r we get 2s = 4s^2 s = 1/2 so statement 2 is also sufficient hence ans is D but this is not correct _________________

OA is "A". That's only A is sufficient. but I presume that that answer should be "C" because for me r=s , if I substitute in the equation then

1/r + 1/r = 2/r = 4 r = 1/2 and I am able to prove the condition. Although, OG has taken values of r and s to prove that 2nd condition is not sufficient, then why not try to put some values for r and s in the 1st option too? Please help

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.

Hi Bunuel, Could you kindly explain statement 2 clearly. From the choice, we come to the conclusion that r=s=1/2. Cant this be sufficient to answer the question? In that case, it should be (D) right.????

OA is "A". That's only A is sufficient. but I presume that that answer should be "C" because for me r=s , if I substitute in the equation then

1/r + 1/r = 2/r = 4 r = 1/2 and I am able to prove the condition. Although, OG has taken values of r and s to prove that 2nd condition is not sufficient, then why not try to put some values for r and s in the 1st option too? Please help

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.

Hi Bunuel, Could you kindly explain statement 2 clearly. From the choice, we come to the conclusion that r=s=1/2. Cant this be sufficient to answer the question? In that case, it should be (D) right.????

The question asks: is \frac{1}{r}+\frac{1}{s}=4 ?

(2) says r = s. So, our questions becomes: is \frac{1}{r}+\frac{1}{r}=4? --> is r=\frac{1}{2}? Notice it's not given, in contrast we are asked to answer this.

Now, if r=\frac{1}{2}, then the answer is YES but if r\neq\frac{1}{2}, then the answer is NO. Do we know what r is actully equal to? No. So, this statement is NOT sufficient.

Re: If rs#0, is 1/r + 1/s = 4 ? [#permalink]
10 Aug 2014, 17:00

Hi Bunuel, Could you kindly explain statement 2 clearly. From the choice, we come to the conclusion that r=s=1/2. Cant this be sufficient to answer the question? In that case, it should be (D) right.????[/quote]

The question asks: is \frac{1}{r}+\frac{1}{s}=4 ?

(2) says r = s. So, our questions becomes: is \frac{1}{r}+\frac{1}{r}=4? --> is r=\frac{1}{2}? Notice it's not given, in contrast we are asked to answer this.

Now, if r=\frac{1}{2}, then the answer is YES but if r\neq\frac{1}{2}, then the answer is NO. Do we know what r is actully equal to? No. So, this statement is NOT sufficient.

Hope it's clear.[/quote]

Can you explain that please ? if we applied the second answer's approach on statement one :

if r= 1/2 and s=1/2 …….. > then r+s=4rs = 1/2 + 1/2 = 4*1/2*1/2 …. but if r=2 and s=2 the …> 2+2 not equal to 4*2*2

If rs#0, is 1/r + 1/s = 4 ? [#permalink]
12 Aug 2014, 07:04

Expert's post

shagalo wrote:

Can you explain that please ? if we applied the second answer's approach on statement one :

if r= 1/2 and s=1/2 …….. > then r+s=4rs = 1/2 + 1/2 = 4*1/2*1/2 …. but if r=2 and s=2 the …> 2+2 not equal to 4*2*2

this question is confusing !!!!!

Your question is not clear.

(1) says that r + s = 4rs. Why are you plugging number for which r + s does not equal to 4rs ? Also, the question asks whether r + s = 4rs and (1) directly answers this. Why even plug? _________________